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BIOGRAPHIES 


DISTINGUISHED  SCIENTIFIC  MEN. 


/^  COT..  COLL. 

TJBRARY 

N.YOKK. 


yust  Published. 
ARAGO'S    BIOGRAPHIES 

OF 

DISTINGUISHED    SCIENTIFIC    MEN. 

FIRST    SERIES       ftl.OO. 


BIOGRAPHIES 


DISTINGUISHED  SCIENTIFIC  MEN, 


By    FRANCOIS    ARAGO, 

MEMBER  OF  THE  INSTITUTE. 


TRANSLATED   BY 

ADMIRAL  W.  H.  SMYTH,  D.C.L.,  F.R.S.,  &c. 
THE  REV.  BADEN  POWELL,  M.A.,  F.R.S.,  &c. 

AND 

ROBERT  GRANT,  Esq.,  M.A.,  F.R.A.S. 


SECOND  SERIES. 


BOSTON: 
TICKNOR   AND    FIELDS. 

M  nccc  LIX. 


RIVERSIDE,      CAMBRIDGE: 
PRINTED   BY   H.    0.    HOUGHTON   AND  COMPANY. 


■5S" 


TJBRAm: 

N.YOIIK. 


CONTENTS. 


CARNOT. 

PAQE 

Childhood  of  Carnot. — His  Education 1 

Entrance  of  Carnot  into  the  School  of  Mezieres  as  Sec- 
ond Lieutenant  of  Engineers 8 

Carnot  a  First  Lieutenant  on  Service  in  Fortresses  •  •  •  •       9 
The  first  Communication  between  Carnot  and  the  Acad- 
emy of  Sciences. — Air-Balloons 10 

Eloge  of  Vauban  by  Carnot. — His  Discussions  with  M.  de 

Montalembert 13 

Essay   on  Machines. — New   Theorem  on   the   Loss  of 

Power , 21 

Carnot  a  Politician  and  one  of  the  Judges  of  Louis  XVI.  30 
Carnot  a  Member  of  the  Committee  of  Public  Safety-  •  •  33 
Carnot  entrusted  with  the  Organization  and  Direction  of 

our  Armies 44 

Carnot  on  the  Field  of  Battle  at  Wattignies 50 

Statistics  of  the  Operations  of  the  Armies 54 

Carnot,  named  by  Fourteen  Departments,  enters  the 
Council  of  the  Elders,  and  then  the  Executive  Direc- 
tory.— Hoche  sent  to  La  Vendue,  Moreau  and  Jourdan 
to  the  Rhine,  and  Bonaparte  to  Italy 54 


30805 


vi  CONTENTS. 

PAGE 

Publication  of  the  Work  entitled  "  Reflections  on  the 

Metaphysics  of  the  Infinitesimal  Calculus  " 60 

Carnot  being  "  Fructidorise  "  is  obliged  to  recur  to  Flight. 
— He  is  erased  from  the  List  of  the  Institute,  and  suc- 
ceeded by  General  Bonaparte 65 

18th  Brumaire. — Return  of  Carnot  to  France. — His  Nom- 
ination to  be  Minister  of  War. — His  Dismissal. — His 

Appointment  to  the  Tribunate ^S 

Publication  of  the  Geometry  of  Position 77 

Carnot  Inventor  of  a  New  System  of  Fortification 84 

Publication  of  the  Treatise  on  the  Defence  of  Fortresses.     94 

Carnot  an  Academician 95 

Events  of  1813. — Carnot  appointed  to  the  Command  at 

Antwerp ^^ 

Conduct  of  Carnot  during  the  Hundred  Days 100 

Carnot  in  Exile.— His  Death 102 

Portrait  of  Carnot. — Anecdotes  relative  to  his  political 
and  private  Life 104 

MALUS. 
Birth  of  Malus.— His  Literary  Education.— His  Admis- 
sion to  the  Polytechnic  School 117 

Egyptian  Campaign. — Extracts  from  the  Memoranda  of 

Malus 120 

Marriage  of  Malus. — His  Military  Career 133 

Memoir  on  Light. — Composed  in  Egypt 135 

Treatise  on  Analytical  Optics 138 

Memoir  on  the  Refractive  Power  of  Opaque  Bodies.  ...    139 
Malus  gains  the  Prize  proposed  by  the  Academy  for  a 

Mathematical  Theory  of  Double  Refraction 147 

Discovery,  of  Polarization  by  Reflexion 148 

Letter  from  Young  to  Malus 158 


CONTENTS.  Vll 

PAGE 

Invention  of  the  Repeating  Goniometer.. 160 

Mains  a  Candidate  for  the  Academy  of  Sciences.— Situa- 
tions which  he  filled. — His  Death 163 

Character  of  Malus.— Maxims  and  Precepts.— Suscepti- 
bility of  Malus  on  Questions  of  Scientific  Priority 167 

FRESNEL. 

Preliminary  Notice 1^1 

Infancy  of  Fresnel.— His  Entrance  into  the  Polytechnic 
School  and  into  the  Corps  of  Bridges  and  Highways.— 
His  Deposition  for  having  gone  to  join  the  Royal  Army 

at  Palud 175 

Fresnel's  first  Scientific  Papers 183 

Refraction 186 

Interferences 202 

Polarization 217 

Principal  Characteristics  of  the  System  of  Emission  and 
of  that  of  Waves.— Grounds  on  which  Fresnel  was  led 

to  reject  unreservedly  the  System  of  Emission 231 

Light-Houses 263 

Life  and  Character  of  Fresnel. — His  Death 273 

THOMAS   YOUNG. 

Preliminary  Notice 280 

Birth  of  Young. — His  Childhood. — First  Entrance  on  his 

Scientific  Career 282 

Theory  of  Vision 291 

Interferences 298 

Egyptian  Hieroglyphics. — History  of  the  first  Exact  In- 
terpretation given  of  them 313 

Note  by  Translator 325 

Miscellaneous  Works  of  Dr.  Young 329 


Vin  CONTENTS. 

PAOK 

Character  of  Young. — His  Position  as  a  Physician. — His 

Engagement  on  the  Nautical  Almanac. — His  Death-  •   330 
Note  by  the  Author 350 

JAMES   WATT. 

Preliminary  Notice 351 

Infancy  and  Youth  of  James  Watt. — His  Advancement 
to  the  Appointment  of  Engineer  to  the  University  of 

Glasgow 352 

Principles  of  the  Steam-Engine 362 

History  of  the  Steam-Engine  in  Ancient  Times 366 

History  of  the  Steam-Engine  in  Recent  Times 370 

Modern  Steam-Engine 379 

Watt's  Labours  in  the  Steam-Engine 387 

Machines  considered  relative  to  their  Effect  on  the  Wel- 
fare of  the  Working  Classes 407 

Press  for  Copying  Letters. — Heating  by  Steam. — Compo- 
sition of  Water. — Bleaching  by  the  Aid  of  Chlorine. — 
Essay  on  the  Physiological  Effects  that  may  result  from 

Breathing  various  Gases 424 

Watt  in  Private  Life. — Details  of  Events  and  of  his  Dis- 
position.— His  Death. — Numerous  Statues  erected  to 

his  Memory. — Reflections 441 

Academic?  1  Titles  with  which  Watt  was  invested 467 

Appendij^. — Retranslation  of  an  Historical  Note  by  Lord 
Brougham,  on  the  Discovery  of  the  Composition  of 
Water 469 

Note  by  W.  Fairbairn,  F.R.S.  F.G.S 481 


LIVES 


DISTINGUISHED  SCIENTIFIC  MEN. 


CARNOT 


BIOGRAPHY  READ  AT  A  PUBLIC   ASSEMBLY   OP   THE  ACAD- 
EMY OF   SCIENCES,   ON   THE  21ST   OF   AUGUST,  1837. 


CHILDHOOD    OF   CARNOT. — HIS    EDUCATION. 

Lazare-Nicolas-Marguerite  Carnot  was  born  at 
Nolay  (Cote-d'Or),  in  the  ancient  dncliy  of  Burgundy 
that  had  ah-eady  been  the  cradle  of  three  of  the  greatest 
ornaments  of  which  the  Academies  could  boast :  Bossuet, 
Vauban,  and  Buffon.  His  father  was  an  advocate,  and 
exercised  that  noble  profession  with  a  great  deal  of  talent 
(which  is  not  uncommon)  and  with  very  great  disinter- 
estedness (which  is  said  to  be  not  so  common).  The 
advocate,  Claude- Abraham  Carnot,  had  eighteen  children  ; 
so  that,  according  to  the  old  adage,  which  promises  pros- 
perity to  a  numerous  family,  he  might  expect  a  happy 
future  for  each  of  his  children.  Indeed,  at  one  period, 
he  might  have  counted,  in  this  numerous  family,  two  lieu- 
tenant-generals of  the  French  armies ;  a  councillor  at  the 

SEC.    SEU.  1 


2  CARNOT. 

court  of  repeal ;  an  attorney-general  of  the  cour  royale  ; 
the  directress  of  the  hospice  de  Nolay ;  a  municipal  mag- 
istrate much  esteemed  whilst  he  was  administering  the 
affairs  of  his  corporation,  and  still  more  esteemed,  if 
possible,  when,  after  twenty-three  years'  exercise  of  his 
functions,  he  submitted  to  be  brutally  deposed  sooner 
than  fail  in  his  duty.  I  must  mention  that,  like  an  alfec- 
tionate  and  provident  father,  the  advocate  of  Nolay  had 
not  trusted  unreservedly  to  the  virtue  of  the  proverb,  but 
always  presided  personally  over  the  early  education  of 
his  sons.  Lazare  Carnot,  the  subject  of  this  biography, 
only  left  his  father's  house  to  go,  as  it  was  then  called, 
through  his  Rhetoric  and  Philosophy. 

The  childhood  of  those  privileged  men  who,  under 
various  claims,  have  acted  a  brilliant  part  on  the  stage 
of  the  world,  has  always  attracted  the  attention  of  every 
biographer.  The  "know  thyself"  of  an  ancient  philos- 
opher would  be  but  poorly  interpreted  if  only  looked  on 
as  a  maxim  of  prudence ;  the  maxim  is  susceptible  of  a 
juster  and  wider  interpretation :  it  presents  to  us,  I  think, 
the  whole  human  race,  as  a  body,  for  the  most  important 
species  of  study  that  we  can  undertake.  Therefore, 
Gentlemen,  let  us  carefully  examine  how  those  extraor- 
dinary minds  are  indicated,  are  born,  and  grow,  which, 
on  their  complete  development,  are  destined  to  open  out 
for  themselves  unknown  paths.  These  characteristics 
should  be  collected  Avith  all  the  more  interest,  because 
they  become  daily  more  rare.  In  our  modern  schools, 
modelled  on  exactly  the  same  pattern  from  north  to  south 
and  from  east  to  west ;  subjected  to  the  same  regulations 
and  to  a  uniform  discipline ;  where  children  enter  more- 
over at  the  age  of  nine  or  ten  years,  and  do  not  leave 
until  they  are  eighteen  or  twenty,  individual  character  is 


JUVENILE    CA.REER.  3 

effaced,  or  disappears,  or  is  covered  with  the  mask  of 
conventionality.  The  agricuUurist  Avoald  never  go  into 
a  hothouse  to  learn  the  character,  the  form,  or  the 
appearance  of  those  admirable  plants  which  are  the 
ornament  of  our  ancient  forests.  Neither  is  it  in  our 
regiments  that  one  might  hope  to  trace  out  the  true 
types  of  the  peasants  of  Brittany,  Normandy,  Lorraine, 
or  Franche-Comte.  Our  "  school-regiments  "  (if  I  may 
be  allowed  the  expression)  would  lead  moralists  quite  as 
much  astray.  There,  a  sort  of  mean  is  established,  about 
which,  with  very  slight  variations,  all  the  youth  of  the 
present  day  is  grouped.  Is  this  for  good  or  for  evil? 
Far  be  it  from  me  to  open  such  a  discussion  here ;  I 
merely  say  that  such  is  the  fact,  and  this  fact  will  explain 
why  I  have  collected  various  particulars  of  the  childhood 
of  our  colleague,  which  might  otherwise  have  appeared 
trifliug. 

Carnot  was  only  ten  years  old  when  his  mother,  in  a 
journey  to  Dijon,  took  him  with  her,  and,  to  reward  him 
for  the  thoughtful  docility  which  he  always  showed,  took 
him  to  the  theatre.  A  piece  was  represented  that  day, 
in  which  evolutions  of  troops  and  battles  succeeded  one 
another  without  intermission.  The  young  scholar  fol- 
lowed with  sustained  attention  the  series  of  events  which 
were  developed  before  him ;  but,  all  on  a  sudden,  he  gets 
up,  he  is  agitated,  and,  in  spite  of  the  endeavours  of  his 
mother,  calls  out  in  terms  hardly  polite,  to  an  actor  who 
had  just  come  on  the  stage.  This  person  was  the  acting 
general  of  the  troops  on  whose  side  the  young  Carnot 
was  interested  ;  by  his  cries,  the  child  was  warning  the 
unskilful  chief  that  the  artillery  was  badly  placed  ;  that 
the  gunners,  being  without  cover,  must  necessarily  be 
killed  by  the  fii'st  fire  of  musketry  from  the  ramparts  of 


4  CAKNOT. 

the  fortress  which  they  were  about  to  attack  ;  that,  on 
the  other  hand,  by  establishing  the  battery  behind  a  rock, 
which  he  pointed  out,  both  by  word  of  mouth  and  by 
gesture,  the  mei*  would  be  much  less  exposed.  The 
astonished  actors  did  not  know  what  to  do  ;  Madame 
Carnot  was  disti'essed  at  the  disturbance  which  her  son 
was  occasioning  ;  the  audience  burst  out  laughing ;  every 
one  was  puzzled  as  to  the  cause  of  such  an  unusual  criti- 
cism ;  and  the  supposed  frolic  was  nothing  else  than  the 
revelation  of  a  superior  military  talent,  the  first  symptom 
of  that  powerful  genius  which,  despising  beaten  tracks, 
created,  a  few  years  later,  new  tactics,  and  proposed  to 
replace  the  scientifically  and  ingeniously  combined  forti- 
fications of  Vauban,  by  an  altogether  different  system. 

From  the  age  of  twelve  to  fifteen,  Carnot  pursued  the 
course  of  studies  at  the  College  at  Autun.  He  made 
himself  remarkable  there  by  a  lively,  original  turn  of 
mind,  and  by  a  rare  degree  of  intelligence.  He  next  en- 
tered the  "  little  seminary  "  of  the  same  town.  At  six- 
teen years  of  age  he  had  finished  his  Philosophy.  The 
firmness  which  we  shall  find  in  him  in  the  course  of  a 
most  stormy  career,  was  already  the  leading  feature  in 
his  character.  The  timid  professoi's  of  the  seminary  of 
Autun,  had  a  troublesome  experience  of  it  on  the  day 
when  their  scholar  had  to  support  his  thesis. 

This  ceremony  always  took  place  in  public.  Accord- 
in"'  to  regulations,  the  liberality  of  which  would,  at  the 
present  day,  appear  excessive  to  the  authorities  of  our 
universities,  every  one  of  the  audience  had  the  right  of 
making  objections.  This  criticism  might  be  applied  both 
to  the  principles  and  to  the  style.  Thus  the  amour  pi-opre 
of  the  master  ran  as  much  risk  as  that  of  the  pupil,  and 
the  reputation  of  a  large  establishment  lay  at  the  mercy 


JUVENILE    CAREER.  5 

of  some  lioedless  young  fellow.  Thenee  came  the  custom 
of  starting  the  competitors  in  the  arena  accompanied  l)y 
a  Mentor,  who  came  to  the  assistance  of  their  treacherous 
memories,  and  who,  by  a  word  put  in  at  the  proper  mo- 
ment, brought  them  back  into  the  right  path  as  soon  as 
they  began  to  wander  from  it ;  and  the  Mentor  was  often 
himself  drawn  into  the  discussion  on  his  own  account. 
According  to  this  custom,  the  teachers  of  the  Seminary  of 
Autun  were  proceeding  towards  the  salle  des  exercises, 
whei'e  a  lai'ge  concourse  of  people  was  assembled,  when 
the  young  Carnot  signified  his  intention  to  ascend  to  the 
rostrum  alone,  that  he  would  not  be  accompanied  by  a 
prompter,  that  he  would  not  keep  at  all  to  the  routine 
they  had  assigned  him,  and  that  he  would  speak  alone  or 
not  at  all.  This  resolution  was  combated  by  alternate  en- 
treaties and  threats,  but  in  vain  :  they  were  obliged  to 
submit,  whether  they  liked  it  or  not,  to  this  unprecedented 
caprice  of  the  pupil.  However,  the  most  brilliant  success 
soon  justified  it,  even  in  the  eyes  of  the  irritated  profes- 
sors. A  curious  incident  rendered  the  meeting  remark- 
able :  a  lady,  the  wife  of  a  doctor  of  medicine,  became  the 
most  formidable  adversary  of  the  young  rhetorician  :  she 
argued  against  him,  in  Latin,  with  a  force  of  logic,  with 
an  ease,  a  gi-ace,  and  an  elegance  of  expression,  which 
the  more  astonished  Carnot  and  the  audience,  inasmuch 
as  no  indiscreet  display  had  hitherto  made  them  even, 
suspect  that  Madame  I'llomme  had  carried  her  studies 
farther  than  the  Cuisiniere  bourgeoise,  the  Almanack  de 
Idege,  or  the  Petit  Paroissien. 

Carnot  had  so  thoroughly  taken,  not  only  to  the  prin- 
ciple of  religion,  but,  moreover  (and  they  are  not  the 
same  things),  to  the  minute  practices  of  devotion  scrupu- 
lously followed  at  the  little  seminary  of  Autun,  that  some 


6  CARNOT. 

of  his  friends  thought  at  one  time  of  putting  him  into 
holy  orders.  They  were  strengthened  in  this  idea  by  the 
recollection  of  the  great  number  of  ecclesiastical  dignita- 
ries of  which  this  honourable  family  could  boast,  amongst 
whom  figured  canons,  vicaires-ghieraux  of  the  diocese  of 
Chalon,  doctors  of  the  Sorbonne,  and  an  abbe  of  Citeaux. 
However,  the  career  of  military  engineer  carried  the  day, 
and  young  Carnot  was  sent  to  Paris  to  a  special  school, 
there  to  prepare  for  his  examination.  The  comrades 
whom  he  met  there  had  certainly  not  been  brought  up  at 
the  Seminary ;  for  the  profound  piety  of  the  new  scholar, 
of  which  he  would  by  no  means  make  a  mysteiy,  became 
the  subject  of  their  continual  sarcasms.  Sai-casms  are 
not  reasons.  Carnot  was  not  therefore  staggered  by 
them ;  but  he  felt  the  necessity  of  maturing,  by  reflection 
and  study,  ideas  and  sentiments  to  which  his  pure  and 
candid  soul  had  hitherto  given  itself  up  with  perfect  good- 
will and  confidence.  Theology,  then,  became,  for  some 
months,  the  only  occupation  of  an  apprenti-qfficier,  or 
military  novice.  No  one  can  tell  what  was  the  effect  of 
these  meditations  ;  for,  at  all  periods  of  his  life,  Carnot 
cai-efuUy  avoided,  even  in  the  intimacy  of  the  domestic 
circle,  any  discussions, — nay,  more,  any  simple  conversa- 
tions— I'clating  to  religion.  We  only  know  that  he  pro- 
fessed principles  now  adopted  by  all  good  and  enhghtened 
minds.  "  Universal  tolerance,"  said  he,  when,  proscribed 
and  wandering  in  a  foreign  land,  he  had  to  ward  off  the 
spiteful  darts  of  calumny, — "universal  tolerance,  that  is 

the  dogma  which  I  decidedly  profess I  abhor 

fanaticism,  and  I  beheve  that  the  fanaticism  of  irreligion, 
brought  into  fashion  by  such  men  as  Marat  and  Pere 
Duchesne,  is  the  most  fatal  of  all.  We  must  not  kill  men 
to  force  them  to  believe :  we  must  not  kill  them  to  pre- 


JUVENILE    career;  7 

vent  their  believing ;  let  us  compassionate  the  weaknesses 
of  others,  since  every  one  has  his  own  ;  and  let  us  allow 
prejudices  to  wear  away  by  time  when  we  cannot  obviate 
them  by  reason." 

After  theology,  scientific  studies,  especially  those  of 
geometry  and  algebra,  had  their  turn,  and,  as  at  Nolay 
and  Autun,  his  success  was  rapid  and  brilliant.  M.  de 
Longpre,  director  of  the  preparatory  school,  was  ac- 
quainted with  D'Alembert.  The  illustrious  geometer  was 
not  above  going  amongst  very  young  scholars,  to  encour- 
age rising  merit  by  his  approbation.  In  one  of  his  visits 
he  particularly  distinguished  Carnot,  and  addressed  to 
him  flattering  and  prophetic  words,  which  our  colleague 
would  repeat  with  emotion,  even  during  those  periods 
when  fortune  had  rendered  him  one  of  the  arbiters  of  the 
destinies  of  Europe. 

Perhaps  this  is  an  opportunity.  Gentlemen,  for  re- 
gretting that,  in  our  society,  such  as  half  a  century  of 
revolutions  has  made  it,  the  personal  intercourse  which 
formerly  existed  between  the  professors  and  distinguished 
scholars  of  great  schools,  has  totally  disappeared,  and  has 
become  indeed,  to  a  certain  degree,  impossible.  Now-a- 
days,  at  the  hour  set  down  in  the  programmes,  illustrious 
men  of  learning  or  of  literature  arrive  in  spacious  am- 
phitheatres. A  crowd  is  waiting  for  them.  During  entire 
hours,  all  that  is  profound,  intricate,  or  new,  in  science  or 
literature,  is  developed  with  system,  clearness,  and  elo- 
quence ;  but,  the  lesson  finished,  the  professor  retires, 
without  even  knowing  the  names  of  those  who  have 
listened  to  him.  Nevertheless,  in  the  midst  of  such  an 
audience  (I  will  confine  myself,  Gentlemen,  to  a  single 
example),  Fourcroy  found,  in  an  apothecary's  boy  who 
had  come  furtively  to  hear  him,  the  devoted,  exact,  in- 


8  CARNOT. 

defatigable,  and  ingenious  cooperator  whom,  by  these 
traits,  each  of  you  has  ah-eady  recognized — he  discovered 
Vauquelin ! 

ENTRANCE     OF     CARNOT     INTO     THE     SCHOOL     OP     ME- 
ZIERES    AS    SECOND    LIEUTP:NANT    OP    ENGINEERS. 

At  the  time  when  Carnot  quitted  the  estabhshment  of 
M.  de  Longpi'e,  the  "  ordonnance  "  in  virtue  of  wliich  a 
genealogist  cooperated  witli  a  geometer  in  the  examina- 
tion of  the  future  oihcers  of  engineers  was  not  in  force. 
In  1771  any  Frenchman  might  still  be  admitted  at  the 
school  of  Mezieres  without  showing  any  parchments,  on 
condition  always  that  neither  his  father  nor  mother  had 
endeavoured  to  enrich  their  family  and  their  country  by 
commerce  or  by  manual  labour.  The  young  aspirant 
displayed  unusual  mathematical  knowledge  before  the 
examiner,  Bossut.  His  father,  in  obedience  to  the  sad 
exigencies  of  the  period,  proved  on  his  part  that  no  ship 
of  his  had  ever  been  to  distant  countries  to  exchange  the 
fruits  of  the  French  soil  or  of  French  industry,  for  pro- 
ductions reserved  by  nature  to  other  climates  ;  that  his 
hands  had  never  put  together  the  movable  types  of 
Gutenberg,  even  for  the  purpose  of  reproducing  the 
Bible  or  the  Gospel;  that  he  had  not  personally  co- 
operated in  the  construction  of  any  of  those  admirable 
instruments  which  measure  time,  or  which  sound  the 
depths  of  space. 

After  legal  proof  of  these  negative  merits,  young 
Carnot  was  declared  of  sufficiently  good  family  to  wear 
an  epaulette,  and  received  without  delay  that  of  a  second 
lieutenant. 

Decorated  with  this  so-much-desired  epaulette,  Carnot, 
at  the  age  of  eighteen  years,  came  to  the  School  of  En- 


A    FIRST    LIEUTENANT    ON    SERVICE.  ■       9 

gineers.  There,  under  the  auspices  of  Monge,  he  doubt- 
less cultivated  descriptive  geometry  and  the  physical 
sciences  with  his  habitual  success  ;  but  on  this  point  it 
must  be  owned,  we  are  reduced  to  mere  conjecture  ;  for 
in  carrying  to  an  extreme  the  natural  desire  to  conceal 
from  strangers  the  knowledge,  then  but  little  spread, 
of  the  art  of  making  and  destroying  fortifications,  the 
celebrated  school  of  M(^zieres  had  been  made  a  sort  of 
conclave  of  which  the  secrets  were  never  penetrated  by 
the  profane. 

CARNOT    A    FIRST    LIEUTENANT    ON    SERVICE    IN    FOR- 
TRESSES. 

On  the  12th  of  January,  1773,  Carnot,  having  become 
a  first  lieutenant,  was  sent  to  Calais.  The  works  of  a 
place  where  the  periodical  oscillations  of  the  ocean  add 
a  new  and  important  condition  to  the  already  very  com- 
plicated data  of  the  problem  of  fortification,  were  very 
interesting  to  the  young  officer.  He  thus  overleaped 
without  hindrance,  the  passage,  generally  so  troublesome, 
from  learned  theories  to  tiresome  practice ;  from  the 
brilliant  illusions  which  amuse  us  in  schools,  to  the  sad 
realities  of  life. 

The  Memorial  de  Saint  Helene  says  that  in  his  youth 
"  Carnot  was  looked  on  by  his  comrades  as  an  original." 
This  title  Napoleon  had  borrowed  from  Carnot  himself. 
I  find  it  in  the  answer  to  Bailleul,  but  explained  and 
commented  on,  and  deprived  of  that  vagueness  which 
leaves  it  to  be  taken  either  as  a  compliment  or  a  reproach. 
Carnot,  at  twenty  years  of  age,  was,  to  the  officers  of  the 
garrison  of  Calais,  an  "  original,"  or  a  "  philosojiher," 
(these  words  were  equivalent,)  because  he  did  not  join 
them  either  in  their  turbulence  or  in  any  of  their  wild 
1* 


10  CARNOT. 

pranks ;  because  he  passed  his  time  in  the  libraries 
rather  than  at  the  cafe  ;  because,  he  read  Thucydides, 
Polybius,  and  Cnesav,  rather  than  the  licentious  works  of 
that  2:)eriod  ;  because,  if  he  were  intimate  with  the  Prince 
de  Croy,  Commandant-General  of  Picardy,  it  was  not  for 
the  sake  of  obtaining  leave  from,  or  alleviations  of,  duty, 
but  in  order  to  assist  him  in  delicate  geographical  re- 
searches, and  to  work  at  charts  of  the  Southern  Hemi- 
sphere, showing  the  latest  nautical  discoveries.  Carnot, 
nevertheless,  was  anything  but  an  ill-natured  judge  of 
others.  Severe  towards  himself,  he  had  an  inexhaustible 
fund  of  indulgence  to  every  one  else.  He  employed  his 
hours  of  leisux'e  or  relaxation  in  composing  little  poems, 
all  impressed  with  a  gentle  and  social  gayety.  To  have 
quoted  ballads  in  the  biography  of  a  geometer  would 
certainly  have  had  great  novelty,  and  this  weak  merit, 
quite  within  my  grasp,  had  almost  pei'suaded  me  to  do 
so  ;  a  little  reflection  has  caused  me  to  give  it  up.  A 
great  poet  in  our  country  having  stamped  that  nature  of 
composition  with  his  immortal  seal,  song  should  no  longer 
be  lightly  quoted. 

THE     FIRST     COMMUNICATION     BETWEEN     CARNOT    AND 
THE    ACADEMT    OF    SCIENCES. AIR-BALLOONS. 

The  first  direct  communication  between  Carnot  and 
the  Academy  of  Sciences  (this  fact  Avill  be  a  novelty  to 
every  one)  was  brought  about  by  a  problem  which  not 
only  has  not  yet  been  solved,  but  which,  according  to 
many  physical  philosophers,  appears  as  if  it  never  can 
be — "  the  problem  of  guiding  balloons." 

Scientific  discoveries, "even  those  from  which  mankind 
might  expect  the  greatest  advantages — such,  for  instance, 
as  those  of  the  mariner's  compass  and  the  steam-engine^ 


ON    AIR-BALLOONS.  11 

were  received  on  their  first  appearance  with  disdainful 
indifference.  PoUtical  and  military  events  exclusively 
enjoy  the  privilege  of  exciting  the  public.  There  have 
been,  however,  two  exceptions  to  this  rule.  You  will  all 
know  by  this  hint,  that  I  allude  to  America  and  aii--bal- 
loons,  Christopher  Columbus  and  MontgoMer.  The  dis- 
coveries of  these  two  men  of  genius,  so  different  hitherto 
in  their  results,  had,  at  their  birth,  similar  fortunes. 
Gather,  in  fact,  from  the  Historia  del  Almirante  the 
marks  of  the  general  enthusiasm  which  the  discovery  of 
certain  islands  excited  amongst  the  Andalusians,  the 
Catalonians,  the  Arragonese,  and  the  Castilians ;  read 
the  account  of  the  unheard-of  honours  which  they  hast- 
ened to  render,  as  well  in  the  largest  cities  as  in  the 
smallest  hamlets,  not  only  to  the  leader  of  the  enterprise, 
but  even  to  the  very  sailors  of  the  caravels  La  Santa 
Maria,  La  Pinta,  and  La  Nina,  which  were  the  first  to 
reach  the  western  shores  of  the  Atlantic ;  you  may  then 
save  yourselves  the  trouble  of  searching  in  the  writings 
of  the  period  what  sort  of  sensation  air-balloons  pro- 
duced amongst  our  compatriots :  the  processions  at  Se- 
ville and  Barcelona  were  faithful  representations  of  the 
fetes  which  took  place  at  Lyons  and  Paz*is.  In  1783, 
just  as  it  happened  two  centuries  before,  warm  imagina- 
tions were  not  at  the  trouble  of  confining  themselves  to 
the  limits  of  facts  or  of  probabilities.  In  the  one  instance, 
there  was  not  a  Spaniard  who  did  not  wish,  after  the  ex- 
ample of  Columbus,  himself  also  to  tread  lands  where, 
in  a  few  days,  he  might  collect  as  great  a  quantity  of 
gold  and  precious  stones  as  was  formerly  the  possession 
of  the  richest  potentates.  In  France  each  individual, 
following  the  favourite  direction  of  his  ideas,  made  dif- 
ferent but  charming  applications  of  the  new  faculty — I 


12  CARNOT. 

had  almost  said  of  the  new  organs — which  man  had  just 
I'eceived  from  the  hands  of  Montgolfier.  The  {physical 
philosopher,  transported  into  the  region  of  meteors,  and 
catching  Nature  in  the  act,  penetrated  at  a  glance  the 
mysteiy  of  the  formation  of  lightning,  of  snow,  and  of 
hail.  The  geographer,  profiting  by  a  favourable  wind,  was 
to  explore,  without  danger  or  fatigue,  as  well  those  polar 
zones  which  the  accumuhited  ice  of  centuries  seems  to 
wish  to  conceal  for  ever  from  our  curiosity,  as  those 
central  parts  of  Africa,  New  Holland,  Java,  Sumatra, 
and  Borneo,  forbidden  to  our  enterprises  not  less  by  a 
deadly  climate  than  by  the  fierce  animals  and  tribes 
which  live  there.  Certain  generals  thought  it  an  urgent 
duty  to  study  the  systems  of  fortification  and  artillery 
which  it  would  be  necessary  to  oppose  to  enemies  moving 
in  balloons ;  others  elaborated  new  principles  of  tactics 
applicable  to  aerial  battles.  One  would  say  that  projects 
such  as  these,  which  might  have  been  fathered  on  Ariosto, 
should  certainly  have  satisfied  the  most  adventurous  and 
enthusiastic  spirits :  such  was  not  the  case,  however. 
The  discovery  of  balloons,  notwithstanding  the  brilliant 
accessories  with  which  each  one  enthusiastically  sur- 
rounded it,  appeared  to  be  only  the  forerunner  of  still 
greater  discoveries  ;  henceforward  nothing  was  to  be  im- 
possible to  one  who  had  conquered  the  atmosphere.  This 
idea  was  continually  reproducing  itself;  it  put  on  every 
shape  ;  youth  seized  it  with  joy ;  old  age  made  it  the 
text  of  a  thousand  bitter  i-egrets.  See  the  Marechale  de 
Villeroi,  an  octogenarian  and  an  invalid :  she  is  led  to 
one  of  the  windows  of  the  Tuileries  almost  by  force,  for 
she  does  not  believe  in  balloons  ;  the  balloon  neverthe- 
less detaches  itself  from  its  moorings ;  our  colleague, 
Charles,  seated  in  tlie  cradle,  gaily  salutes  the  spectators, 


£loge  op  vauban.  13 

and  soars  majestically  into  the  air.  Oh  !  on  the  instant 
passing  without  transition  from  the  most  complete  in- 
credulity to  an  unbounded  confidence  in  the  powers  of 
the  human  mind,  the  old  Marechale  falls  on  her  knees, 
and,  her  eyes  bathed  in  tears,  gasps  forth  these  sad 
words  :  "  Yes,  it  is  decided,  now  it  is  certain  ;  they  will 
discover  the  secret  of  never  dying,  but  it  will  he  when  I 
am  dead  !  " 

Carnot,  being  of  a  rigorous  turn  of  mind  (though  he 
was  not  yet  eighty  years  of  age),  took  good  care  not  to 
go  so  far  as  the  Marechale  de  Villeroi.  Nevertheless,  he 
appeared  in  the  ranks  of  the  enthusiasts.  He  then  be- 
lieved, and  always  did  so  afterwards,  in  the  possibility  of 
directing  balloons,  and  consequently  in  the  applications 
which  science  and  the  art  of  war  had  hoped  from  them. 
The  archives  of  the  Academy  ought  to  contain  a  paper 
in  which  Captain  Carnot  of  the  engineers  submitted  to 
the  authorities  an  arrangement  of  light  oars,  which,  in 
his  opinion,  should  attain  the  desired  end.  This  paper 
has  not  yet  been  discovered.  I  will  continue  my  re- 
searches for  it,  and  if  the  work  seems  likely  to  add  to 
the  reputation  of  our  fellow  academician,  the  public  shall 
not  be  deprived  of  it.  Perhaps  I  shall  join  with  it  a 
memoir  of  the  same  nature,  also  unpublished,  by  another 
academician,  the  illustrious  Meunier. 

ELOGE    OP    VAUBAN    BY    CARNOT. HIS    DISCUSSIONS 

WITH    M.    DE    MONTALEMBERT. 

A  certain  literary  society  of  a  very  small  town  once 
on  a  time  gave  itself  the  title,  on  its  own  full  authority, 
of  Daucjliter  of  the  French  Academy.  Voltaire  thought 
that  they  should  not  refuse  it  this  title :  "  Indeed,  I 
esteem   her,"  said   he,  "  as   a   very   virtuous   daughter. 


14  CARNOT. 

since  she  has  never  given  occasion  for  any  talk  about 
her." 

Such  an  epigram  would  not  have  been  applicable  to 
the  Academy  of  Dijou.  This  celebrated  society  did  not 
shun  the  public  gaze,  either  when  it  proposed  the  ques- 
tion, "  Whether  the  reestablishment  of  the  arts  and 
sciences  had  contributed  to  the  refinement  of  manners," 
nor,  more  especially,  when  it  rewarded  the  discourse  in 
which  Jean-Jacques  pronounced  in  the  negative.  Time 
has  done  ample  justice  to  the  paradox ;  but  it  ought  not 
to  have  effaced  the  remembrance  of  the  generous  pro- 
ceeding which,  in  giving  to  Rousseau  an  unexpected 
celebrity,  attached  him  for  ever  to  the  brilliant  career  in 
which  he  met  with  competitors  and  rivals,  but  not  with  a 
master. 

To  the  merit  which  I  have  just  related,  the  Academy 
of  Dijon  can  add  that  of  having  called  forth  the  first  pro- 
duction of  Carnot's  which  the  press  took  possession  of, — 
the  Eloge  of  Vauban. 

The  intrepidity,  the  disinterestedness,  and  the  science 
of  the  illustrious  marshal  had  already  received,  from  the 
tongue  of  Fontenelle,  an  homage  to  which  it  seemed 
difficult  to  add.  What  speech  indeed  could  more 
Avorthily  characterize  a  military  life  than  these  few 
figures  ?  "  Vauban  caused  work  to  be  done  at  300  for- 
tresses ;  he  constructed  33  new  ones ;  he  conducted  53 
sieges ;  he  was  present  at  140  actions  of  importance." 
And  does  not  this  other  sentence  seem  as  though  bor- 
rowed from  Plutarch  ?  "  The  morals  of  Vauban  held 
out  pei'fectly  against  the  most  brilliant  dignities,  and 
never  even  wavered.  In  a  word,  he  was  a  Roman 
whom  it  seemed  as  if  our  age  had  stolen  from  the  best 
times  of  the  Repu])lic  !  " 


ELOGE    OF    VAUBAN.  15 

The  eloge  from  which  these  two  passages  are  taken 
had  always  appeared  to  me  so  eloquent  and  true,  that,  at 
the  moment  when  I  first  discovered  an  oi'ation  on  Vau- 
ban  amongst  tlie  productions  of  our  colleague,  I  burst 
out  into  heartfelt  abuse  at  the  academic  programme 
which,  taking  advantage  of  the  inexperience  of  a  young 
man,  had  exposed  him  to  so  formidable  a  comparison. 
Indeed,  I  should  not  have  been  more  uneasy,  if  I  had 
discovered  that  Carnot  had  endeavoured  to  rewrite  La 
Mecanique  of  Lagi'ange,  Athalie,  or  the  Fables  of  La 
Fontaine.  These  fears  were  superfluous.  The  Bur- 
gundian  members  of  the  Academy  of  Dijon  were  right 
in  thinking  that  the  Burgundian  Vauban  might  still  be- 
come an  interesting  subject  of  study,  even  after  the  bril- 
liant portrait  traced  by  Fontenelle.  And,  in  truth,  the 
Secretary  of  the  Academy  of  Sciences  had  prudently 
left  in  the  shade  one  of  the  finest  points  of  the  illustrious 
marshal. 

It  would  seem  that  the  eloge  of  Vauban,  from  the  pen 
of  an  officer  of  engineers,  must  consist  principally  of  an 
exact  appreciation  of  the  means  of  attack  and  defence 
with  which  the  illustrious  marshal  endowed  the  art  of 
■vvar.  This  was  not  the  plan,  howevei",  which  Carnot 
adopted.  It  was  principally  for  the  qualities  of  the 
heart,  for  virtue,  and  for  patriotism,  that  Vauban  seemed 
to  him  worthy  of  admiration.  "  He  was,"  said  he,  "  one 
of  those  men  whom  nature  gives  to  the  world  formed 
entirely  for  benevolence  ;  gifted,  like  the  bee,  with  an 
innate  activity  for  the  general  welfare  ;  who  cannot 
separate  their  lot  from  that  of  the  Republic,  and  who, 
intimate  members  of  society,  live  and  flourish,  or  suffer 
and  languish,  with  it." 

Prince  Henry  of  Prussia  was  present  at  the  assembly 


16  CARNOT. 

of  the  Academy  of  Dijon,  at  which  the  eloge  of  Vauban 
was  read  and  rewarded.  He  expressed,  in  the  most 
unequivocal  terms,  the  great  pleasure  that  the  discourse 
had  given  him  ;  and  assured  the  author  of  his  profound 
esteem,  both  verbally  and  in  writing.  Piqued  with 
emulation,  the  Prince  de  Conde,  who  presided  at  the 
assembly,  as  governor  of  Burgundy,  outdid  the  marks  of 
favour  which  were  shown  to  the  young  engineer  officer 
by  the  brother  of  Frederic  the  Great. 

Had  Carnot  then  flattered  the  prejudices  of  the  nobles  ? 
Were  his  principles  in  1784  so  different  from  those  which 
afterwards  directed  all  his  actions,  as  necessarily  to  re- 
ceive the  suffrages  of  the  great  ?  Listen,  Gentlemen, 
and  judge ! 

The  Dime  Roy  ale  (the  King's  Tithe),  that  writing 
which,  under  Louis  XIV.,  brought  about  the  complete 
disgrace  of  Vauban,  and  of  which  Fontenelle  had  the 
prudence  not  even  to  mention  the  title,  in  enumerating 
the  works  of  the  illustrious  marshal,  was  called  by  Car- 
not a  simple  and  pathetic  exposition  of  facts ;  a  woi^c  in 
which  "  every  thing  is  striking  by  its  precision  and  truth- 
fulness." The  assessment  of  the  taxes,  in  France,  in  the 
eyes  of  the  young  officer,  was  "  barbarous  ;  "  the  manner 
of  gathering  them  "  more  barbarous  still."  According  to 
him,  the  true  object  of  a  government  is  to  oblige  every 
individual  of  the  State  to  labour;  the  method  which  he 
points  out  for  obtaining  this  result  would  be  (I  quote 
from  the  text)  to  cause  riches  to  pass  from  those  hands 
Avhere  they  are  superfluous,  into  those  where  they  are 
necessary.  Carnot  gives  his  adhesion  unreservedly  to 
this  precept  of  Vauban's  ;  the  laws  ought  to  prevent  the 
frightful  misery  of  the  one  class  and  the  excessive  opu- 
lence of  the  other ;  he  sets  his  face  against  the  odious 


ON    EQUALIZING    PROPERTY.  17 

multiplicity  of  privileges  from  which  the  more  numerous 
classes  of  the  population  had  then  so  much  to  suffer ; 
finally,  after  having  divided  mankind  into  two  categories, 
the  workers  and  the  idlers,  he  goes  so  far  as  to  say  of 
these  latter,  who  alone,  according  to  him,  have  been 
taken  into  account  in  the  constitution  of  modern  society, 
that  "  they  do  not  begin  to  be  useful  till  the  moment  in 
wliich  they  die,  for  they  do  not  vivify  the  earth  except 
by  reentering  it."  Such,  Gentlemen,  are  the  bold 
opinions  wdiich  an  Academy  rewarded  in  1784 ;  which 
called  forth  from  Buffon,  who  certainly  cannot  be  ac- 
cused of  having  been  an  innovator  in  matters  of  govern- 
ment, these  words  so  flattering  to  the  successful  orator : 
— "  Your  style  is  noble  and  flowing ;  you  have  done,  sir, 
an  agreeable  and  useful  work ;  "  and  which  inspired  the 
brother  of  an  absolute  king  with  the  desire  of  attaching 
Carnot,  Avhose  "  friend  "  he  declared  himself  to  be,  to  the 
service  of  Prussia ;  which  gained  for  the  young  officer 
the  favour  of  the  prince  whom  Worms  and  Coblentz 
witnessed  a  few  years  afterwards  at  the  head  of  the 
emigration  !  Who  then  will  dare  to  call  our  revolution 
of  1789  an  effect  without  a  cause,  a  meteor  of  whose 
arrival  there  had  been  no  warning  ?  The  moral  trans- 
formations of  society  are  subjected  to  the  law  of  con- 
tinuity; they  rise  and  grow  hke  the  productions  of  the 
earth,  by  imperceptible  gradations. 

Each  century  develops,  discusses,  and  adapts  to  itself, 
in  some  degree,  truths — or,  if  you  prefer  it,  principles — 
of  which  the  conception  belonged  to  the  preceding  cen- 
tury ;  this  work  of  the  mind  usually  goes  on  without 
being  perceived  by  the  vulgar ;  but  when  the  day  of 
application  ai'rives,  when  principles  claim  their  part  in 
practice,  when  they  aim  at  penetrating  into  political  life, 


18  CARNOT. 

the  ancient  interests,  if  they  have  only  this  same  anti- 
quity to  invoke  in  their  favour,  become  excited,  resist, 
and  struggle,  and  society  is  shaken  to  its  foundations. 
The  tableau  will  be  complete,  Gentlemen,  when  I  add 
that,  in  these  obstinate  conflicts,  it  is  never  the  principles 
that  succumb. 

Carnot,  as  I  have  already  remarked,  had  but  lightly 
touched  on  the  technical  part  of  Vauban's  works,  in  his 
^loge  ;  yet,  in  the  few  sentences  which  he  Avrote  on  this 
subject,  he  took  occasion  to  say  that  "  a  certain  vulgar, 
ignorant,  person  "  took  an  erroneous  view  of  fortification 
in  reducing  it  to  the  art  of  tracing  on  paper  lines  sub- 
jected to  certain,  more  or  less,  systematic  conditions. 
These  words,  in  their  general  sense,  seemed  as  if  they 
might  have  passed  unnoticed ;  but  an  unfortunate  con- 
currence of  circumstances  gave  to  them  an  importance 
which  was  not  foreseen,  and  still  less  desired  by  their 
author.  In  1783,  a  general  of  infantry,  member  of  this 
Academy,  M.  le  Marquis  de  Montalembert,  published, 
under  the  title  o?  Perpendicular  Fortification,  an  entirely 
new  system  of  defence  of  fortresses.  This  system  was 
outrageously  opposed  by  almost  the  whole  corps  of  mili- 
tary engineers.  The  scion  of  an  illustrious  family,  the 
general  officer  of  the  French  army,  the  academician, 
might  assuredly,  without  too  much  vanity,  believe  him- 
self not  included  in  the  ignorant  vulgar  that  the  author 
of  the  eulogy  had  lightly  designated ;  but  M.  de  Mont- 
alembert was  determined  to  apply  these  expressions  to 
himself,  and  to  revenge  himself  he  published  an  edition 
of  Vauban's  eloge  accompanied  by  notes,  in  which  offence 
and  gross  affront  were  carried  to  the  utmost.  There  was 
enough  in  this  pamjihlet  to  upset  the  mind  of  a  young 
man  a  thousand  times ;  nevertheless,  under  these  diffi- 


MERITS    OF    MONTALKMRERT.  19 

cult  circumstances,  Carnot  already  showed  himself  such 
as  he  always  was  afterwards — frank,  just,  and  completely 
insensihle  to  undeserved  abuse. 

"  If  your  suspicions  wdre  well  founded,"  wrote  he  to 
his  fiery  antagonist,  "  I  should  have  forgotten  the  first 
duties  of  propriety  and  decency  ;  I  should  have  been 
wanting,  above  all,  in  the  infinite  respect  which  military 
men  owe  to  a  distinguished  general :  be  assured  that 
there  is  not  a  single  officer  of  engineers  who  has  not 
learnt  with  the  same  pleasure,  from  M.  le  Marquis  de 
Montalembert,  how  to  fortify  places  well,  as  from  the 
brave  D'Esse  to  defend  them  well." 

The  appositeness  and  delicacy  of  this  quotation  will  be 
appreciated  when  I  mention  that  the  brave  D'Esse,  who, 
in  1543,  after  three  months  of  an  heroic  resistance,  com- 
pelled the  whole  forces  of  the  emperor  to  raise  the  siege 
of  Landrecies,  was  an  ancestor  of  M.  de  Montalembert. 

Moderation  and  politeness  are  almost  infallible  means 
of  success  against  violence  and  affront ;  moreover,  in  the 
quarrels  of  the  press,  they  must  often  be  looked  upon  as 
the  simple  result  of  calculation,  and  as  proofs  of  ability. 
But  Carnot's  letter  allowed  no  misapprehension  as  to  the 
sincerity  of  his  sentiments.  "  Your  work,"  he  wrote  to 
him  who  had  just  criticized  so  bitterly  the  principle,  the 
style,  and  I  might  almost  add,  the  punctuation,  of  his 

^loge,  "  your  work  is  full  of  genius How  that 

your  casemates  are  known  and  proved,  fortification  will 
put  on  a  new  face  ;  it  u'ill  become  a  new  art.  It  w^ill  be 
no  longer  allowable  to  employ  the  revenues  of  the  State 
to  construct  something  tolerable,  when  you  have  taught 

us   to    cousti'uct  something  good Although  the 

corps  of  engineers  has  not  the  advantage  of  possessing 
you,  we  do  not  the  less  consider  that  we  have  a  right  to 


20  CAKNOT. 

reckon  you  amongst  its  most  illustrious  members.  Who- 
ever extends  our  knowledge,  whoever  furnishes  us  with 
new  means  of  being  useful  to  France,  becomes  our  com- 
rade, our  chief,  and  our  benefactor."  M.  de  Montalem- 
bert  did  not  resist  such  explicit  and  flattering  testimony. 
The  most  formal  disavowal  of  the  unlucky  pamphlet 
quickly  followed  Carnot's  answer  ;  on  the  other  hand,  it 
must  be  confessed  that  the  higher  authorities  of  the  en- 
gineers were  so  irritated  at  the  praises  which  a  simple 
captain  had  allowed  himself  to  bestow  on  systems  which 
they  had  authoritatively  rejected,  that  a  "  lettre  de 
cachet"  and  the  Bastille  signified  to  our  member  that, 
on  the  eve  of  our  great  revolution,  liberty  of  discussion, 
that  precious  conquest  of  modern  philosophy,  had  not 
yet  penetrated  amongst  military  usages.  Such  rigour 
seems  inexplicable,  even  when  one  makes  every  allow- 
ance for  the  requirements  of  esprit  de  corps  and  the  sus- 
ceptibilities of  self-esteem ;  Carnot  had  shown  himself, 
indeed,  both  in  his  dloge  and  in  his  letter  to  Montalem- 
bert,  the  warmest  defender  of  the  department  to  which 
he  belonged,  and  which,  said  he,  "  professes  to  sacrifice 
its  time  and  its  life  for  the  State."  Had  this  man  then, 
I  demand,  forgotten  the  duties  of  his  position,  who,  when 
called  on  to  judge  between  the  services  of  a  regimental 
ofRcer  and  those  of  the  engineer  on  whom  devolves  the 
dangerous  honour  of  tracing  parallels,  of  commanding  in 
the  trench,  or  of  directing  the  head  of  a  sap,  expressed 
himself  so  nobly  :  "  The  officer  of  engineers  is  in  the 
midst  of  peril,  but  he  is  there  alone  and  silent ;  he  sees 
death,  but  he  must  gaze  on  it  with  coolness ;  he  may  not 
rush  on  it  like  the  heroes  of  battle  ;  he  sees  it  appi'oach 
with  tranquillity ;  he  seeks  the  spot  where  the  lightning 
bursts  forth,  not  to  act  but  to  observe  ;  not  to  get  excited, 
but  to  deliberate." 


POWEK    OF    MACHINES.  21 

Perhaps,  Gentlemen,  I  should  not  have  insisted  at 
such  length  on  this  painful  episode  in  Carnot's  life,  if  I 
had  not  had  opportunity  of  perceiving  how  far  removed 
are  such  times  from  ours  ;  if  I  had  not  seen,  when  ac- 
companying our  most  illustrious  officers  of  engineers  in 
the  inspection  of  some  fortified  towns,  in  the  discussion 
of  the  amelioration  they  might  be  susceptible  of,  the 
simple  sous-lieutenant  freely  oppose  his  ideas,  reflections, 
and  systems,  with  full  liberty,  to  the  opinions  of  the  gen- 
erals ;  surrender  only  after  having  been  victoriously 
refuted  ;  and  come  forth  from  the  animated  contest,  not, 
as  formerly,  to  go  to  the  Bastille,  but  with  fresh  chances 
of  advancement. 

Those  on  whom  the  duty  devolves  of  incessantly 
referring  to  the  ameliorations  of  which  our  social  state 
is  susceptible,  would  become  discouraged.  Gentlemen,  if, 
when  occasion  presents  itself,  we  did  not  show  the  public 
that  their  endeavours  have  been  sometimes  crowned  with 
success. 

ESSAY  ON  MACHINES. NEW  THEOREM  ON  THE  LOSS 

OF  POWER. 

The  first — nay,  more,  the  principal — scientific  produc- 
tion of  Carnot,  bears  the  date  of  the  year  1783  ;  it  is 
entitled  Essay  on  Machines  in  general. 

They  who  would  seek  in  the  essay  of  our  member  the 
technical  description  or  special  study  of  any  one  of  the 
machines  in  particular,  simple  or  composite,  from  which 
man  has  been  able  to  derive  so  many  advantages,  would 
lalioiir  to  no  purpose.  Such  was  not,  indeed,  the  end 
which  the;  author  had  in  view. 

jV  macliine,  considei-ed  generally,  is  the  assemblage  of 
a  more  or  less  considerable  number  of  fixed  or  movable 


22  CARNOT. 

pieces,  by  the  aid  of  which  forces  of  all  sorts  ordinarily 
produce  effects  which  their  direct  action  could  not  bring 
about.  Take,  for  instance,  the  stone-mason  with  his 
hand  on  the  handle  of  a  very  simple  machine,  the  winch 
of  the  lifting-jack  or  the  roller  ;  he  turns  about  enormous 
blocks,  or  inclines  them  to  suit  his  convenience,  or  raises 
them  to  the  summit  of  the  highest  buildings,  when,  with- 
out the  machine,  he  could  not  stir  them  a  hair's  breadth. 

At  sight  of  these  effects,  the  ignorant  make  great  out- 
cry at  the  marvel ;  they  persuade  themselves  that  ma- 
chines multiply  force,  and  this  false  idea,  radically  false, 
leads  them  into  fantastic  and  generally  very  complicated 
conceptions,  which  take  away  an  immense  quantity  of 
capital  every  year,  in  pure  loss,  from  agriculture,  and 
manufacturing  industry,  and  commerce. 

With  a  force  of  any  nature  whatsoever,  that  which 
must  be  valued  in  money,  that  which  the  fabricator  buys 
from  the  engineei*,  may  be  easily  referred  to  a  very  sim- 
ple effect,  of  which  every  one  has  a  clear  idea.  Let  the 
force  be  supposed  directly  applied  to  the  raising  of  a 
weight ;  the  height  to  which  the  force  raises  the  weight 
in  a  certain  time  is  observed,  and  these  two  data  from 
experiment,  the  weight  and  the  height,  multiplied  together 
form  a  product  which  is  the  exact  value  of  the  force  em- 
ployed. This  product,  indeed,  for  a  given  time  and  the 
same  height,  cannot  be  augmented  or  diminished  with- 
out the  force  augmenting  or  diminishing  in  the  same 
proportion  ;  so  tluit,  for  example,  if  it  becomes  double,' 
triple,  or  decuple,  it  is  the  result  of  the  force  being  mul- 
tiplied by  two,  tliree,  or  ten. 

The  product,  which  gives  the  direct  measure  of  a 
force,  serves  equally  to  measure  it  when  it  exercises  its 
action  against  a  resisting  body  by  an   intermediate  ma- 


POWER    OF    MACHINES.  23 

chine ;  well,  endow  this  machine,  if  you  please,  with  the 
power  of  thought  and  all  the  perfections  imaginable,  and 
the  product  of  the  weight  multiplied  by  the  height  it  will 
have  passed  through  in  a  given  time,  will  be  exactly 
equal  to  that  obtained  by  the  employment  of  the  same 
force  without  any  intermediate  operation.  The  real 
effect,  then — or,  to  speak  more  strongly,  the  effect  of 
any  machine  when  properly  estimated — will  never  sur- 
pass that  which  the  motive  force  was  capable  of  pro- 
ducing naturally.  Doubtless  you  can,  if  you  like,  with 
a  machine,  raise  enormous  masses,  of  millions  or  thou- 
sands of  millions  of  pounds  ;  but  since  the  product  of  the 
weight,  multiplied  by  the  height,  must  remain  constant, 
the  height  to  which  these  masses  can  be  raised  in  a 
minute  will  be  millions  or  thousands  of  millions  of  times 
smaller  than  that  to  which  your  hand  might  have  raised 
one  pound  in  the  same  time. 

Every  one  will  now  understand  the  true  meaning  of 
that  aphorism  in  mechanics.  Machines  lose  in  time  or 
velocity  what  they  gain  in  power  !  Give  me  a  point  of 
support  situated  outside  the  earth,  cried  Archimedes, 
and  I  will,  with  the  aid  of  a  lever,  raise  this  earth,  so 
large  and  massive,  by  the  mere  effort  of  my  hand.  The 
exclamation  of  the  immortal  geometer  was  marvellously 
characteristic  of  machines,  in  so  far  as  they  give  to  man 
the  means  of  realizing  effects  otherwise  millions  of  mil- 
lions of  times  beyond  his  natural  strength  ;  but  antiquity 
would  no  doubt  have  admired  it  much  less  if  any  one, 
analyzing  phenomena  more  closely,  as  we  have  just 
done,  had  added  :  Yes,  doubtless,  mathematically  speak- 
ing, with  his  fulcrum  and  lever  Archimides  might  raise 
the  globe  ;  but,  after  forty  million  centuries  of  continu- 
ous effort   (for  such  a  calculation  is  not,  at  the  present 


24     .  CARNOT. 

day,  beyond  the  limits  of  science),  the  movement  effected 
would  be  hardly  the  breadth  of  a  liair. 

If  the  ideal  machine,  the  machine  endowed  with  all 
imaginable  perfections,  adds  nothing  to  the  force  which 
puts  it  in  action,  at  any  rate  it  takes  nothing  away  from 
it ;  it  transforms  the  effects  by  rigorous  equivalents.  It 
is  not  thus  with  a  real  machine ;  in  this  case  the  power 
and  the  resistance  communicate  with  one  another  by 
means  of  pieces  which  we  had  supposed  inflexible,  and 
which  are  not  so  ;  by  means  of  chains  and  cords  whose 
roughness  cannot  but  be  injurious ;  the  movable  parts, 
moreover,  turn  in  collars  or  sockets  where  great  friction 
takes  place ;  all  these  causes  united  absorb  in  pure  loss 
a  very  noticeable  part  of  the  motive  force ;  so  that  the 
effect  of  a  machine  must  always  be  inferior  to  that  which 
would  have  been  engendered  by  the  power  acting  directly 
on  the  i-esistance. 

These  results  of  theory,  which  are,  moreover,  com- 
pletely confirmed  by  experience,  yet  allow  that,  under 
certain  points  of  view,  some  particular  machine  may  be 
recommended  without  paradox  ;  that  it  may  be  useful 
and  often  even  indispensable.  For  instance,  considerations 
of  solidity  or  ornament  necessitate  the  carrying  to  the  sum- 
mit of  certain  edifices  blocks  of  stone  or  marble  whose 
weight  is  beyond  the  strength  of  the  most  vigorous  work- 
man ;  suppress  the  windlass  and  analogous  machines, 
and  one  man  will  no  longer  be  able  to  execute  the  work 
which  the  architect  has  conceived  ;  it  will  be  necessary 
to  unite  the  strength  of  thousands  of  arms  at  the  same 
point ;  the  narrowness  of  space  will  prevent  that ;  the 
character  of  grandeur  will  disappear  from  all  the  monu- 
ments of  architecture  ;  the  triumphal  arch,  the  palace, 
will  only  be  constructed,  like  the  humble  cottage,  of 
little  rough  stones. 


TIIEOKEM    IN    MECHANICS.  25 

You  see,  Gentlemen,  tliat  there  are  cases,  it  cannot 
be  too  often  repeated,  in  which  we  must  resign  ourselves, 
whether  we  will  or  no,  to  the  loss  of  force  consequent  on 
machines,  since,  without  their  help,  certain  works  would 
become  impossible. 

The  losses  of  force  which  depend  on  the  flexibility  of 
the  materials  of  which  machines  are  composed,  on  the 
roughness  of  cords,  and  on  friction,  had  been  remarked 
by  the  most  ancient  mechanicians  ;  modern  ones  have 
gone  farther  ;  their  experiments  enable  them  to  appreci- 
ate these  losses  and  value  them  in  numbers  with  tolerable 
exactness.  Science  had  arrived  thus  far,  when  Cai-not 
published  his  Essay.  In  this  work,  our  member,  looking 
on  machines,  and  even  more  generally  on  every  system 
of  movable  bodies,  from  an  entirely  new  point  of  view, 
indicates  a  cause  unperceived,  or  at  any  rate  imperfectly 
analyzed,  by  his  predecessors,  and  which  in  certain  cases 
must  also  give  rise  to  considerable  losses ;  he  shows  that 
we  ought,  by  all  means,  to  avoid  abrupt  changes  of 
velocity.  Carnot  does  more  ;  he  finds  the  mathematical 
expression  of  the  loss  of  active  force  which  such  chano-es 
occasion ;  he  shows  that  it  is  equal  to  the  active  force 
by  which  all  the  various  bodies  of  the  system  would  be 
animated,  if  each  of  them  were  endowed  with  the  com- 
plete velocity  which  it  lost  at  the  instant  of  the  abrupt 
change  being  affected. 

Such  is.  Gentlemen,  the  enunciation  of  the  principle 
which,  under  the  name  of  "  Carnot's  Theorem,"  plays  so 
great  a  part  in  the  calculation  of  the  effect  of  machines. 

This  beautiful  and  valuable  theorem  is  now  well 
known  to  all  engineers  ;  it  guides  them  in  practice,  and 
secures  them  from  the  gross  faults  committed  by  their 
precursors. 

SEC.    SEK.  2 


26  CARNOT. 

To  give  an  idea  of  its  importance  to  the  generality  of 
tlae  world,  I  should  be  inclined  to  say,  notwithstanding 
the  fantastic  appearance  of  the  comparison,  that  Carnot 
has  extended  to  the  material  world  a  proverb  whose 
truth  was  only  established,  before  his  time,  in  the  moral 
world ;  that  "  much  noise  *  and  little  work  "  is  a  saying 
henceforth  quite  as  applicable  to  the  effective  labours  of 
machines,  as  to  the  enterprises  of  certain  individuals 
whose  petulance  gives  rise  to  the  hope  of  wonders  des- 
tined not  to  be  realized.  In  addressing  men  of  learning, 
I  would  beg  them  to  distinguish  carefully  between  the 
invention  of  the  material  organs  by  whose  aid  forces 
transmit  their  action  from  one  point  to  another,  and  the 
discovery  of  those  primordial  truths  which  are  applicable 
indistinctively  to  all  imaginable  systems ;  I  will  endeav- 
our to  show  that  in  this  first  respect  the  ancients  wei-e 
perhaps  not  inferior  to  us.  The  screw  of  Archimedes, 
the  series  of  toothed  wheels  of  Ctesibius,  the  hydrostatic 
fountains  of  Heron  of  Alexandria,  the  steam  rotating 
machine  of  the  same  engineer,  a  great  number  of  war- 
like machines,  and  amongst  them  the  balista,  might  all  be 
brought  forward  to  strengthen  my  view.  In  the  field  of 
theoretical  truths,  on  the  contrary,  the  preponderance  of 
the  moderns  would  show  itself  incontestable. f  There 
we  should  see  successively,  in  all  their  brilliancy,  in  Hol- 

*  The  proverb  does  not  fit  at  all  neatly,  unless  "noise  "  be  taken 
to  mean  "  iiTegnlarity  ; "  some  good  machines  are  very  noisy. — 
Translator. 

t  The  question  is  rather  unfairly  stated  ngainst  the  ancients;  for 
Arago  speaks  as  if  Archimedes,  &c.,  had  only  made  their  machines, 
and  not  been  masters  of  the  principles,  which  involved  as  much  pri- 
mordial truth  as  any  other  discoveries.  A  fairer  distinction  seems  to 
be,  that  the  moderns  launched  out  into  realms  where  theory  alone 
couhl  point  out  the  wny ;  the  ancients  were  led  on  by  experiment  and 
observation.  —  Translator. 


THEOREM    IN    MECHANICS.  27 

land,  Stevin  and  Huyghens ;  in  Italy,  Galileo  and  Tor- 
ricelli  ;  in  England,  Newton  and  Maclaurin  ;  in  Swit- 
zerland, Bernouilli  and  Euler  ;  in  France,  Pascal,  Va- 
rignon,    D'Alembert,  Lagrange,  and  Laplace. 

Well,  Gentlemen,  those  are  the  illustrious  personages 
amongst  whom  Carnot  made  a  place  for  himself  by  his 
beautiful  theorem. 

Perhaps,  indeed,  I  ought  to  be  afraid  that,  by  insisting 
any  longer  on  the  inconvenience  of  abrupt  changes,  I 
may  inspire  my  audience  with  the  desire  that  I  should, 
notwithstanding  every  inconvenience,  pass  "abruptly"  to 
another  subject ;  nevertheless,  I  will  hazard  a  few  more 
words. 

We  have  just  been  talking  frequently  of  lost  force  ;  the 
expression  is  correct  when  we  compare  the  actual  effect 
of  a  machine  with  that  which  it  might  have  produced  if, 
all  other  circumstances  remaining  the  same,  the  construc- 
tor had  carefully  avoided  sudden  changes  of  speed  ;  but 
it  must  not  be  imagined  that  any  force,  or  fraction  of  a 
force,  can  be  ever  annihilated,  in  the  grammatical  accep- 
tation of  the  word  ;  all  that  which  is  not  found  in  the 
useful  effect  produced  by  the  motive  power,  nor  in  the 
amount  of  foi'ce  which  it  retains  after  having  acted,  must 
have  gone  towards  the  shaking  and  destroying  of  the 
machine. 

This  last  remark  was  necessary  for  the  appreciation  of 
the  eminent  and  incontestable  services  which  Carnot's 
theorem  has  already  rendered  and  will  render  more  and 
more  to  art  and  industry.  If  I  were  not  afraid  of  the 
incredulity  which  would,  at  first  sight,  attach  itself  to  my 
words,  I  would  add  that  this  same  theorem  of  analysis  and 
mechanics  has  also  played  a  great  part  in  the  numerous 
events  of  our  Revolution,  whose  character  Carnot's  deter- 


28  CARNOT. 

minations  were  able  to  change.  However,  I  have  said 
too  much  not  to  complete  the  idea. 

In  my  youth,  encouraged  by  the  good-will  and  friend- 
ship with  which  Carnot  was  kind  enough  to  honour  me, 
I  sometimes  took  the  liberty  of  calling  his  recollection  to 
those  great  epochs  of  our  revolutionary  annals,  when 
parties,  in  their  frenzied  convulsions,  were  destroyed, 
conquered,  or  merely  appeased,  by  abrupt  and  violent 
measures,  by  real  coups  d'etat.  Then  I  would  ask  our 
colleague  how  he,  alone  amongst  all  the  others,  had  con- 
stantly hoped  to  arrive  at  the  goal  without  shocks,  and 
without  infringement  of  the  laws  ;  his  answer,  always 
the  same,  had  become  deeply  graven  on  my  memory ; 
but  what  was  my  surprise  when,  emerging  one  day  from 
the  round  of  studies  which  a  young  astronomer  should 
always  impose  on  himself,  I  found,  word  for  word,  this 
constant  answer  which  we  have  just  been  discussing  in 
the  enunciation  of  a  theorem  of  mechanics ;  when  I  saw 
that  our  colleague  had  always  discoursed  with  me  on  the 
political  organization  of  society  precisely  in  the  same 
manner  as  he  speaks  in  his  work  of  a  machine,  in  which 
abrupt  changes  necessarily  involve  great  losses  of  force, 
and  sooner  or  later  bring  about  the  comj^lete  dislocation 
of  the  system  !  * 

Can  it  then  be  true,  Gentlemen,  that  in  the  weakness 
of  the  human  race,  the  loftiest  spirits  have  been  so  little 
convinced  of  the  goodness  and  truth  of  the  determinations 
which  their  hearts  inspire  them  with,  that  they  have 
found  it  necessary  to  confirm  and  corroboi'ate  them  with 
more  or  less  forced  assimilations  ? 

*  This  pai-allel  cannot  be  deemed  exact:  in  the  Revolution  they 
wanted  to  destroy  one  machine  altogether,  and  supply  quite  another; 
so  the  rules  applicable  to  steady  machinery,  or  government,  do  not 
apply. —  Translalor. 


THEOREM    IN    MECHANICS.  29 

This  doubt  will  not  astonish  you  if  I  add  that  one  of 
the  learned  men  whose  works  have  conferred  the  great- 
est distinction  on  this  Academy,  conducted  himself  on  all 
difficult  occasions  (so  we  are  to  believe)  according  to  the 
following  assuredly  very  convenient  maxim  :  "  Water 
takes  exactly  the  form  of  the  vase  which  contains  it  ;  a 
wise  mind  should  as  faithfully  model  itself  on  the  circum- 
stances of  the  moment." 

I  might  quote  also  another  of  our  colleagues,  equally 
celebrated,  of  whom  a  certain  personage  asked  one  day 
in  my  presence,  by  what  secret  he  had  passed  through 
the  terrible  periods  of  our  civil  discords  without  mishap  : 
"  Every  country  in  a  state  of  revolution,"  answered  he, 
"is  a  carriage  of  which  the  horses  have  taken  the  bit 
between  their  teeth  ;  to  wish  to  stop  the  horses  is  to  rush 
on  a  catastrophe  from  gayety  of  heart ;  he  who  leaps  from 
the  carriage  exposes  himself  to  being  crushed  under  the 
wheels ;  the  best  plan  is  to  abandon  one's  self  to  the 
movement,  and  shut  one's  eyes  ;  so  did  I !  "* 

In  the  work  whose  analysis  has  carried  me  farther 
than  I  expected,  Carnot  has  devoted  some  lines  to  the 
question  of  perpetual  motion  !  He  shows  not  only  that 
every  machine,  of  whatever  form,  abandoned  to  itself  will 
stop,  but  he  moreover  assigns  the  moment  at  which  that 
must  happen. 

The  arguments  of  our  colleague  are  excellent  ;  no 
geometer  will  dispute  their  exactness  ;  may  we  yet  hope 
that  they  will  nip  in  the  bud  the  numerous  projects  which 
every  year,  or  rather  "every  spring,"  sees  burst  into 
flower  ? 

This  is  what  we  cannot  hope  for.     The  contrivers  of 

*  If  the  horses  could  not  be  stopped,  surely  an  attempt  should  be 
made  to  guide  them. —  Translator. 


30  CARNOT. 

perpetual  movements  would  no  more  comprehend  the 
work  of  Carnot,  than  the  discoverers  of  the  quadrature 
of  the  circle  or  the  trisection  of  the  angle  understand  the 
geometry  of  Euclid.*  Science  is  not  needed  by  them  ; 
they  owe  their  discovery  to  a  sudden  supernatural  inspi- 
ration. Moreover,  nothing  discourages  them,  nothing  un- 
deceives them ;  take,  for  example,  that  artist,  otherwise 
highly  estimable,  who,  without  perceiving  any  thing  inno- 
cently burlesque  in  the  terms  of  his  request,  begged  me 
to  go  and  see  ^^wliy  all  his  perpetual  movements  had 
stopped.'^ 

CARNOT    A    POLITICIAN    AND    ONE    OF    THE    JUDGES    OF 
LOUIS    XVI. 

Carnot  was  one  of  the  first  officers  of  the  French  army 
that  loyally  and  enthusiastically  embraced  the  regenera- 
tive views  of  the  National  Assembly.  Nevertheless,  the 
annals  of  the  Revolution  only  commence  making  mention 
of  him  in  1791. 

Certain  writers  wrongly  take  the  spirit  of  proselytism 
as  the  just  measure  of  the  sincerity  of  political  convic- 
tions ;  they  do  not  understand  how  a  retired  and  studious 
life  may  ally  itself  to  a  profound  desire  for  social  reforms  ; 
Carnot's  two  years  of  inaction  seem  to  them  quite  a  phe- 
nomenon. Now,  guess  how  they  deemed  it  advisable  to 
explain  it.  They  place  our  member  amongst  the  emigres 
of  Coblentz  ;  thus  his  republican  tendencies  would  only 
date  from  the  period  at  which  he  furtively  reentered 
France.  I  will  not  oflfend  you.  Gentlemen,  by  refuting 
such  a  ridiculous  supposition. 

In  1791  Carnot  was  in  garrison  at  Saint-Omer,  and 

*  Not  quite  a  just  comparison.  There  is  no  reason  why  these  geo- 
metric feats  must  be  impossible,  as  is  the  case  with  perpetual  motion. 
—  Translator. 


A    POLITICIAN.  31 

there  married  Mademoiselle  Dupont,  daughter  of  a  mili- 
tary administrator  born  in  that  country.  His  political 
principles,  the  moderation  of  his  conduct,  and  his  varied 
knowledge,  shortly  procured  him  the  honour  of  represent- 
ing the  department  of  the  Pas-de-Calais  in  the  Legisla- 
tive Assembly.  From  this  period  Carnot  gave  himself 
up  entirely  to  the  imperious  duties  which  were  imposed 
on  him,  either  by  the  choice  of  his  fellow-citizens,  or  the 
voice  of  his  colleagues.  The  public  character  almost 
entirely  absorbed  that  of  the  geometer :  this  last  only 
showed  itself  henceforth  at  long  intervals. 

Here,  Gentlemen,  two  roads  present  themselves  to  me  ; 
one  is  smooth  and  open,  the  other  bordered  by  precipices. 
If  I  listened  to  some  persons  whose  good  will  towards  me 
has  rendered  them  timid,  I  should  not  hesitate  to  choose 
the  first.  To  take  the  other  would  be  to  incur,  I  am 
well  aware,  the  reproach  of  imprudence  and  blindness. 
Heaven  keep  me  from  supposing  that  I  am  strong  enough 
to  struggle  against  such  clear  and  decided  opinions ;  but 
wretched  considerations  of  self-love  will  always  vanish 
from  my  sight  before  the  sentiment  of  duty.  Now,  I  ask, 
should  I  not  deeply  wound  the  public  conscience  if,  in  this 
area  consecrated  to  the  arts,  letters,  and  sciences,  I  con- 
fined myself  to  speaking  of  Carnot  as  an  academician  ? 
Without  doubt  one  might,  whilst  developing  before  you 
the  long  series  of  discoveries  of  this  or  that  illustrious 
savant,  endowed  during  his  life  with  the  title  of  senator, 
legitimately — very  legitimately — cry  out  that  posterity 
would  not  preserve  any  recollection  of  functions  without 
effect,  and  which,  moreover,  descending  from  one  degra- 
dation to  another,  had  ended  by  reducing  themselves  to  a 
monthly  communication  with  the  treasury ;  but  it  would 
be  an  antinational  and  ungrateful  act  to  apply  such  words 


32  CARNOT. 

to  the  great  shade  of  Carnot.  I  am  desired,  wished,  and 
almost  ordered  to  do  this.  Well !  I  consent,  I  will  not 
speak  of  the  drama  whose  "denouement"  was  the  tragic 
death  of  the  successor  of  a  hundred  kings,  and  the  over- 
throw of  the  monarchy  ;  nevertheless  I,  a  decided  parti- 
san of  the  abohtion  of  the  punishment  of  death,  do  not 
perceive  the  supposed  difficulties  of  position  which  should 
have  hindered  me  from  abandoning  myself  here  publicly 
to  the  inspirations  of  my  conscience  ;  nor  do  I  see  any- 
better,  why  I  should  have  abstained  from  rendering  this 
assembly  aware  of  the  deep  aversion  which  I  profess  for 
every  political  decree  issued  by  a  political  body.  Must  I 
say  it,  in  a  word  ? — a  fraternal  solicitude  for  the  memory 
of  Carnot  did  not  appear  to  me  to  require  the  sacriSce 
which  is  imposed  upon  me.  Is  it  forgotten  how  contem- 
poraneous history  would  have  furnished  me  with  accusing 
documents  against  the  thousand  courtiers  whose  inter- 
ested, hypocritical,  and  antinational  manoeuvres  cast  the 
monarch  into  a  labyrinth  without  exit,  caused  him  to  be 
unanimously  declared  culpable  by  the  national  represen- 
tatives, and  were  much  more  instrumental  than  the  ardent 
deraocratical  ideas  of  the  Convention  in  rendering  the 
catastrophe  of  the  21st  of  January  inevitable  ?  If  from 
these  high  moral  considerations  I  had  descended  to  a 
minute  appreciation  and  technical  discussion  of  facts, 
such  as  one  has  to  submit  to  a  court  of  appeal  or  of  re- 
peal, I  should,  in  company  with  all  upright  minds — with 
our  Daunou,  for  example, — have  found  the  illegality  of 
the  celebrated  trial,  less  in  the  nature  of  the  sentence, 
less  in  the  severity  of  the  punishment  inflicted,  than  in 
the  very  composition  of  the  tribunal,  or  in  the  usurpation 
of  power  which  had  given  birth  to  it.  Now,  Gentlemen, 
— and  this  is  a  point  I  should  not  have  failed  to  remark 


COMMITTEE    OF    PUBLIC    SAFETY. 


33 


on, — when  the  Convention  was  investing  itself  with  the 
riglit  of  pronouncing  on  the  fate  of  Louis  XVI.  ;  wlien 
after  this  stroke  it  was  regulating  its  jurisprudence  ;  when 
it  was  simultaneously  attributing  to  itself  the  functions  of 
accuser  and  judge,  Carnot  was  absent  from  Paris ;  he 
was  fulfilling  with  the  armies  one  of  those  important 
missions,  the  difficulties  of  which  his  ardent  pati'iotisni 
always  found  the  secret  of  surmounting. 

CAUNOT    A    MEMBER    OF    THE    COMMITTEE    OP    PUBLIC 

SAFETY. 

The  concession  which  was  required  of  me,  if  I  con 
formed  exactly  to  it,  nevertheless  authorizes  me  to  show 
myself  less  docile  on  the  subject  of  another  period  of 
Carnot's  life,  which  is  still  more  stormy  and  difficult. 
Let  us  avoid — I  wiUingly  consent  to  it — carrying  our  at- 
tention back  to  certain  irritating  phases  of  our  civil  dis- 
cords ;  for  my  own  part,  I  will  only  put  one  condition  on 
it ;  that  is,  that  the  memory  of  none  of  our  members 
shall  suffisr  by  it.  Well,  Gentlemen,  suppose  for  a  mo- 
ment that  I  be  now  silent  concerning  the  "  Member  of 
the  Committee  of  Public  Safety ; "  would  it  not  be  con- 
cluded from  my  silence — nay  more,  would  it  not  be  right 
to  conclude  from  thence — that  I  have  recognized  the 
impossibility  of  repelling  the  violent,  numerous,  and 
trenchant  attacks  of  which  he  was  the  object  ?  These 
attacks  Carnot,  whilst  living,  was  able  to  disdain  ;  in  me, 
on  the  contrary,  it  was  incumbent  to  seek  for  their  origin, 
and  conscientiously  weigh  their  value.  I  say  it  with- 
out exaggeration,  no  human  power  should  have  decided 
me  to  cause  the  name  of  Carnot  to  reecho  here,  unless 
I  had  discovered  the  honourable  and  patriotic  causes  of 
certain  acts  which  the  most  atrocious  of  calumnies,  politi- 

2* 


34  OAKNOT. 

ciil  calumny,  had  soiled  with  its  infected  slaver.  My 
work,  furthermore,  was  not  without  some  difficulties. 
Perhaps  no  one  henceforth  will  have  the  opportunity 
to  reunite  its  elements.  In  a  few  years,  indeed,  the 
colleagues  and  fellow  labourers  of  Carnot,  from  whom 
I  have  been  able  to  gather  some  lights  and  evidences, 
will  have  paid  the  debt  of  nature. 

In  1793  the  convention  was  the  only  organized  power 
in  the  State,  capable  of  opposing  an  effective  dyke 
against  the  overflow  of  enemies,  who  came  from  all 
parts  of  Europe  to  cast  themselves  on  France,  and 
menace  her  nationality.  The  nationality  of  a  people  is 
like  honour :  the  slightest  wound  to  it  becomes  mortal. 
Such  were,  Gentlemen,  the  sentiments  of  very  many 
members  of  the  Convention,  whose  memory  France  re- 
veres ;  such  were  the  ties  which  attached  them  to  the 
perilous  post  whither  election  had  called  them. 

In  creating  the  "  Committee  of  Public  Safety,"  (6th 
April  1793,)  the  Convention  had  reserved  to  itself  the 
choice  of  its  members.  Up  to  the  famous  31st  of  May, 
it  counted  only  neutral  members,  or  at  any  rate  such  as 
were  strangers  to  the  factions  of  the  Assembly  who  were 
combating  each  other  to  the  death.  After  several  partial 
renewals  it  was  composed,  on  the  11th  September  1793, 
of  Robespierre,  Saint-Just,  Couthon,  Collot  d'Herbois, 
Billaud-Varennes,  Prieur  (of  the  Marne),  Prieur  (of  the 
Cote-d'Or),  Carnot,  Jean-bon  Saint- Andre,  Barere,  He- 
rault  de  S(;chelles,  and  Robert  Lindet. 

The  Convention,  when  vt  delegated  such  great  powers 
to  the  Committee  of  Public  Safety,  desired  that  every 
affair  should  be  a  subject  of  profound  discussion  and  de- 
liberation in  that  committee ;  that  the  majority  of  voices 
should  decide.     The  decisions,  to  acquire  the  force  of 


COMMITTEE    OF    PUBLIC    SAFETY.  35 

law,  under  p.ain  of  being  null,  must  be  furnished  with  a 
certain  number  of  signatures.  These  prescriptions  had 
the  greatest  of  all  faults,  that  of  being  completely  im- 
practicable. Man  has  discovered  in  our  days  the  secret 
of  going  ten  times  as  flist  when  he  travels,  of  using  less 
force  when  he  acts,  and  of  casting  his  searching  gaze 
into  the  regions  of  infinity  ;  but  he  has  not  yet  discovered 
the  means  of  reading  a  page  of  manuscript  in  less  time 
than  it  formerly  occupied.  We  must  allow  that  in  that 
respect,  the  most  humble  merchant's  clerk  would  advance 
equally  with  Caesar  or  Cicero,  Descrates  or  Bossuet.  The 
innumerable  dispatches  which  the  Committee  of  Public 
Safety  received  daily,  from  all  points  of  the  frontiers 
menaced  or  invaded,  from  all  the  towns  and  villages  of 
the  interior  where  the  promoters  of  a  new  political  or- 
ganization were  in  violent  conflict  with  the  prejudices 
and  interests  of  the  privileged  classes,  could  not  be  ma- 
turely examined.  Zeal,  activity,  and  devotion  were  not 
sufficient  to  expedite  so  many  weighty  affairs  ;  a  reform ' 
was  indispensable  ;  it  concerned  the  safety  of  France. 
Two  different  ways  presented  themselves :  they  could 
demand  the  reorganization  of  the  Committee,  or  divide 
the  work  amongst  its  various  membei-s.  The  reor- 
ganization of  the  Committee,  in  presence  of  a  powerful 
enemy,  and  in  the  midst  of  unheard-of  difficulties  (such 
as  no  period  of  the  history  of  nations  had  given  an  ex- 
ample of),  would  have  excited  in  the  Convention  new 
ferments  of  disorder,  enervated  its  magic  power,  and 
compromised  the  defence  of  the  territory.  The  division 
of  labour  should  prevail,  and  it  did  prevail.  Carnot 
was  charged  with  the  organization  of  the  armies  and 
with  their  operations  ;  Prieur  (of  the  Cote-d'Or)  with 
arming  them  ;   Robert  Lindet  with  provisioning  them  ; 


36  CARNOT. 

Robespierre,  Saint-Just,  Couthon,  Billaud-Varennes,  and 
Collot  d'Herbois,  reserved  to  themselves  politics,  general 
police,  and  measures  of  security.  In  each  species  of 
subject  one  signature  alone  was  important,  and  .carried 
responsibility  ;  the  others,  though  requii^ed  by  law,  were 
to  be  regarded  as  the  accomplishment  of  a  simple  for- 
mality :  it  was  evident,  indeed,  that  they  would  have  to 
be  given  without  discussion  and  even  without  examina- 
tion. 

Such  were.  Gentlemen,  the  bases  of  the  agreement 
which  Robert  Lindet,  for  his  personal  security,  caused 
to  be  put  down  in  a  written  declaration,  and  by  the  aid 
of  which  the  members  of  the  Committee  of  Public  Safety 
expected  to  be  able,  without  passing  beyond  the  terms  of 
their  mandate,  to  exorcise  the  storms  which  were  menac- 
ing the  country  from  all  sides.  This  confiding  arrange- 
ment will  doubtless  be  blamed :  some  will  cry  out  at  its 
illegality,  others  at  its  imprudence.  I  will  remind  the 
first,  that  the  members  of  the  Committee,  entangled  in  a 
faulty  organization,  were  every  day  at  issue  with  an  im- 
possibility, and  that  the  w^ord  impossible  is  French,  what- 
ever national  amour  propre  may  have  said  of  it  at  a 
period  when  the  admirable  triumphs  of  our  armies  seemed 
to  warrant  all  hyperbolic  speeches.  The  reproach  of  im- 
prudence I  admit  without  reserve.  I  add  that,  on  the 
part  of  Carnot,  this  imprudence  was  voluntary  ;  that  in 
resigning  himself  to  signing,  without  examination,  the 
decisions  of  all  his  colleagues,  he  wittingly  made  the 
greatest  of  all  sacrifices  to  France  ;  that  he  placed  his 
honour  in  the  hands  of  several  of  his  declared  enemies  ; 
that,  counting  eventually  on  the  tardy  justice  of  posterity, 
he  hoisted  that  almost  superhuman  motto  of  one  of  the 
most  powerful  organizations  which  the  Revolution  brought 


COMMITTEE    OF    PUBLIC    SAFETY.  37 

to  land  from  tlie  waves  of  the  people, — that  motto  which 
moreover  every  sincere  patriot  endowed  with  any  warmth 
of  soul  might  avow  :  Perish  my  reputation  sooner  than 
my  country. 

You  will  have  already  understood,  Gentlemen,  that  my 
design  is  to  divide  into  two  distinct  categories  the  mem- 
bers of  the  Committee  of  Public  Safety,  and  the  long 
series  of  its  acts. 

The  terrible  Committee  contributed  powerfully  to  the 
defence  of  the  territory :  thanks  to  the  Committee ! 
There  was  no  other  way  of  resisting  the  thousand  pas- 
sions let  loose,  than  by  vigour  of  determination  ;  by 
energy  of  will ;  by  seizing  everywhere  with  a  grasp  of 
iron  the  barbarians  who,  auxiharies  of  i\\Q  foreigner, 
would  have  torn  out  the  entrails  of  their  country  ;  the 
Committee  showed  itself  energetic  and  vigorous ;  it 
often  showed  the  grasp  of  iron  :  all  praise  to  the  Com- 
mittee ! 

But,  Gentlemen,  firmness  soon  degenerates  into  frenzy  ; 
soon  they  immolate  the  rich  for  the  sole  reason  that  they 
are  rich  ;  soon  terror  reigns  through  France  from  one 
end  to  the  other ;  terror  carries  mourning  and  despair 
without  distinction,  as  well  into  the  family  of  the  com- 
mon soldier  as  into  that  of  the  general ;  she  seizes  her 
victims  equally  in  the  humble  dwelling  of  the  artisan,  as 
in  the  gilded  palace  of  the  former  duke  and  peer :  she 
spares  neither  age  nor  sex  ;  she  strikes  blindly  all  shades 
of  opinion  ;  finally,  adding  dissimulation  to  cruelty,  she 
parodies  the  forms  of  justice  !  Ah  !  Gentlemen,  at  this 
spectacle  the  heart  grows  faint,  and  hope  withers  ;  tlie 
liveliest  and  most  ardent  sympathies  gives  jilace  to  pro- 
found grief. 

I  am  aware  that  attempts  have  been  made  to  explain. 


38  CARNOT, 

even  to  excuse,  those  bloody  saturnalia,  by  referring  them 
to  the  will  of  the  people.  But  if  I  judge  of  the  people 
of  1793,  whom  I  have  not  known,  by  that  which  I  saw 
in  action  in  1830,  the  explanation  is  false.  I  do  not 
hesitate  to  say  so.  The  people  in  a  moment  of  efifer- 
vescence  and  blindness,  sometimes  fall  into  culpable 
actions,  but  it  has  never  associated  itself  with  daily 
barbarities.  It  is  degrading  the  people  to  say,  that  fear 
only  could  drive  it  to  meet  inimical  hordes :  nor  are  its 
sentiments  better  known,  when  it  is  insinuated  that  it 
wished  for  the  death  of  one  of  the  members  of  this 
Academy  who  honoured  France  by  his  genius ;  and  the 
death  of  another  of  our  co-academicians,  who  did  honour 
to  human  nature  by  his  vh-tue^  No,  Gentlemen ;  no ! 
in  the  noble  country  of  France,  the  death  of  Lavoisier, 
the  death  of  Malesherbes,  could  not  be  ordered  by  con- 
siderations for  the  public  good.  No  excuses  for  such 
crimes ;  they  must  be  branded  to-day,  they  must  be 
branded  to-morrow ;  they  must  be  branded  for  ever. 
Devoted  by  sentiment,  by  conviction,  by  the  irresistible 
power  of  logic  to  the  worship  of  liberty,  let  us  repel  far 
from  us  the  execrable  thought,  that  the  scaflfold  is  the 
inevitable  auxihary  of  democracy. 

The  crimes  that  I  have  been  openly  denouncing  have 
been  in  some  measure  personified  by  France,  by  Europe, 
by  the  whole  world :  these  crimes  are  Robespierre ! 
Some  young,  some  estimable  writers,  who  are  now  de- 
spoiling our  revolutionary  annals  with  the  indefatigable 
patience  of  the  Benedictines  of  former  ages,  think  they 
have  discovered  that  public  opinion  is  quite  wrong. 
According  to  them,  llobespierre  and  his  partisans  have 
much  less  contributed  to  the  sanguinary  acts  of  terror, 
than  the  Billaud-Vai'cnnes,  the  Collot  d'Herbois,  or  the 


NOT    A    PARTY    MAN.  39 

Heberts.  There  is  courage,  Gentlemen,  in  coming  for- 
ward as  the  defenders  of  a  man,  who  for  nearly  half  a 
century  has  been  regarded  as  the  symbol,  the  type,  of 
political  cruelty.  On  this  claim  alone  the  new  historians 
hope  to  be  listened  to  without  prejudice :  an  honourable 
character,  joined  to  incontestable  talent,  gives  them  no 
less  a  right  to  the  serious  attention  of  the  public.  For 
my  part,  I  have  no  business  here  to  try  to  pierce  those 
thick  clouds  ;  my  subject  does  not  require  it ;  I  will  ab- 
solve Carnot  from  all  participation  in  great  crimes, 
without  examining  whether  they  should  be  imputed  to 
Collot  d'Herbois,  or  to  Billaud-Varennes,  rather  than  to 
Robespierre,  Saint-Just,  and  Couthon. 

In  no  instance  of  his  long  political  career,  was  Carnot 
a  party-man.  Never  was  he  found  to  try  to  bring  for- 
ward his  opinions,  his  systems,  his  principles,  by  tortuous 
ways  that  honour,  that  justice,  that  probity,  could  not 
have  acknowledged. 

In  reporting  on  the  9th  of  June  1792,  on  the  commis- 
sion charged  to  propose  some  reparation  in  favour  of  the 
families  of  Theobald  Dillon  and  of  Berthois,  who  were 
massacred  by  their  own  troops  before  Lille,  he  does  not 
coquette  with  his  rigorous  duty.  Any  other  man,  in 
such  harassing  times,  might  perhaps  have  thought  it 
requisite  to  consider  the  susceptibility  of  the  army ;  but 
he  seemed  to  think  no  words  too  severe  to  brand  such 
an  odious  act  of  wrong-headedness :  he  exclaimed,  "  I 
will  not  remind  you  of  the  circumstances  of  that  atrocity. 
Posterity,  in  reading  our  history,  will  deem  it  rather  the 
crime  of  a  horde  of  cannibals,  than  that  of  a  free  people." 

In  1792,  some  National  Guards,  under  the  name  of 
confederates,  assembled  in  great  numbers  at  Soissons, 
and  already  formed  there  the  nucleus   of  an  anny  of 


40  CARNOT. 

reserve.  All  at  once  a  report  was  spread  at  Paris,  that 
the  bread  of  those  volunteers  had  been  poisoned,  that 
some  monsters  had  mixed  pounded  glass  with  all  the 
flour  furnished  to  them,  that  two  hundred  soldiers  had 
died  already,  and  the  hospitals  were  overflowing  with 
sick  men.  The  exasperation  of  the  Parisian  populace 
rose  to  its  highest  pitch :  the  depot  at  Soissons  was 
formed  against  the  royal  will ;  the  crime  then  must  be 
imputed  to  the  King,  to  the  Queen,  to  all  their  adherents. 
Before  acting,  they  only  awaited  the  report  of  the  com- 
missary who  had  been  sent  to  the  camp.  This  commis- 
sary was  Carnot.  His  truthful  examination  reduced  all 
this  ^phantasmagoria  to  nothing  :  there  were  no  men  dead  : 
there  were  no  men  sick :  the  flour  was  not  poisoned  ; 
but  some  panes  of  glass,  broken  by  the  wind,  or  by  the 
ball  of  some  recruit,  had  fallen  from  the  window  of  an 
old  church,  and  happened  (not  pulverized,  but  in  large 
pieces,)  to  lie  on  one  single  bag  of  flour.  The  upright 
testimony  of  the  honest  man  calmed  the  popular  tem- 
pest. 

He  was  not  a  party-man  (understood  of  course  in  its 
unfavourable  meaning)  ;  but  one  who,  often  charged 
with  important  missions  to  the  armies  and  to  the  interior, 
fulfilled  his  duties  with  such  moderation,  that  he  could 
safely,  when  circumstances  required  it,  without  fear  of 
being  contradicted,  publicly  render  to  himself  the  testi- 
mony of  never  having  caused  the  arrest  of  any  one.  By 
searching  into  the  offices  of  the  Committee  of  Safety, 
we  should  there  find  equally  clear  proofs  of  the  benevo- 
lent indulgence  of  Carnot  towards  persons  professing 
different  political  ojiinions  from  his,  provided  always 
that  they  were  united  to  honest  dealing,  and  a  warm 
antipathy  to  the  intervention  of  foreigners  in  the  internal 


A    MAN    OF   THE    NATION.  41- 

affairs  of  France.  Thus  we  shall  see,  under  the  name  of 
Michaux,  amidst  the  fellow  labourers  of  our  academician, 
the  celebrated  Dar9on,  who  had  emigrated,  but  returned 
to  his  country.  Still,  what  occasion  is  there  to  drag  our 
audience  through  individual  instances,  when  a  general 
reflection  will  lead  to  the  same  result  ?  The  Convention 
was  the  arena  where  the  chiefs  of  the  factions  that 
divided  the  country,  went  to  combat ;  yet  it  was  in  the 
Clubs  that  they  created  those  adherents,  and  obtained 
that  bodily  strength,  whose  action,  and  even  whose  mere 
presence,  often  sufficed  to  annul  the  effects  of  the  most 
eloquent  discourses.  If  the  Convention  saw  the  thunder- 
cloud burst,  it  was  outside  its  walls  that  it  began  to 
threaten,  that  it  swelled,  that  it  acquired  an  irresistible 
power.  Men  could  not  then  acquire  political  influence 
without  attending  daily  either  at  the  Jacobins  or  at  the 
Cordeliers,  and  mixing  and  taking  part  in  all  their  de- 
bates :  well.  Gentlemen,  Carnot  did  not  belong  to  any 
of  those  associations ;  never  did  a  word  of  his  echo  in 
those  Clubs.  In  those  troublous  times,  Carnot  made 
himself  exclusively  a  man  of  the  nation. 

The  character  was  high,  but  not  without  danger. 
Robespierre  especially  was  jealous  of  him,  and  ex- 
claimed in  one  of  his  harangues :  "  To  have  taken  the 
command  of  all  the  military  operations,  is  decidedly  an 
act  of  egotism  ;  obstinately  refusing  to  take  any  part  in 
the  affairs  of  internal  police,  is  contriving  means  of  ac- 
commodation with  the  enemies  of  the.  country." — He 
said  to  Cambon  on  another  occasion  :  "  I  am  in  despair 
at  not  comprehending  anything  of  the  intersection  of 
lines  and  tints,  that  I  see  on  those  maps.  Ah  !  if  I  had 
studied  the  military  art  in  my  youth,  I  should  not  now 
be  obliged,  whenever  our  armies  are  treated  of,  to  sub- 


42  CARNOT. 

mit  to  the  supremacy  of  the  odious  Carnot."  This 
animosity  began  from  the  epoch  when  our  fellow  aca- 
demician blamed  the  coup  d'etat  (as  such)  under  which 
the  Gironde  fell.  About  the  same  time.  Saint- Just 
accused  him  of  moderatism,  and  demanded  that  he  should 
be  tried  for  having  refused,  while  with  the  army  of  the 
North,  to  put  his  signature  to  the  order  for  arresting 
General  O'Moran.  Carnot  always  came  out  safe  and 
sound  from  these  terrible  crises ;  not  from  a  sentiment 
of  justice  or  affection,  but  because  every  one,  friend  as 
well  as  foe,  felt  the  impossibility  of  I'eplacing  him  effec- 
tually in  his  special  military  character  by  any  other 
conventionalist ! 

Similar  relations  between  the  co-members  of  a  council 
would  now  appear  fabulous  !  Is  it  my  fault  then,  if  our 
weak  patriotism  cannot  conceive  all  the  extent  of  the 
sacrifices  that  our  fathers  imposed  on  themselves  to  save 
our  country  ? 

You  will  remember.  Gentlemen,  that  I  did  not  hesitate 
to  place  in  the  first  rank  of  these  sacrifices  the  obligation 
which  our  colleague  felt,  of  blindly  signing  a  quantity  of 
decrees  issued  by  his  colleagues.  I  have  explained  how 
this  necessity  had  manifested  itself;  well,  it  was  so 
abused,  that  on  one  occasion,  Carnot  was  made  to  sign 
the  order  for  arresting  his  own  secretary ;  another  time 
that  for  arresting  the  r-estaurateur  in  whose  house  he 
took  his  meals.  The  word  infernal  seems  to  me  really 
too  feeble  for  characterizing  such  acts ;  and  yet,  to  the 
honour  of  our  colleague,  we  must  almost  congratulate 
ourselves  that  they  occurred,  since  they  yield  an  insur- 
niountable  and  speaking  proof  of  the  written  arrange- 
ment which  was  agreed  to  in  committee,  in  the  name  of 
the  safety  of  the  country. 


INCLINED    TO    MERCY.  43 

I  had  read,  even  in  royalist  works,  and  I  had  read 
also  in  some  writings  published  by  republicans,  that 
Carnot  had  saved,  in  the  Committee  of  Public  Safety, 
more  men  than  his  colleagues  had  immolated.  Carnot, 
then,  did  not  absent  himself  from  the  meetings  except 
when  military  affairs  entirely  absorbed  his  time  ;  Carnot, 
then,  sometimes  attended  the  delibei-ations  of  the  Com- 
mittee, and  on  those  occasions  innocence  could  depend  on 
an  advocate  full  of  feeling  and  firmness.  Only  a  few 
days  ago,  chance  enabled  me  to  discover  that  the  part  of 
volunteer  defender  was  not  the  only  one  that  Carnot  took 
upon  himself. 

There  is  amongst  you.  Gentlemen,  a  venerable  aca- 
demician equally  versed  in  theoretical  and  in  applied 
mathematics ;  he  has  gloriously  attached  his  name  to 
some  useful  labours,  and  to  some  vast  projects  that  the 
future,  perhaps,  will  realize.  He  has  gone  through  a 
long  career,  without  making,  certainly  without  deserving, 
an  enemy  !  and  yet  his  head  was  once  menaced,  and 
some  wretches  wished  to  make  it  fall,  at  the  very  time 
that  he  was  projecting  one  of  the  scientific  monuments 
that  have  reflected  most  honour  on  the  revolutionary 
era.  An  anonymous  letter  informed  our  colleague  of 
his  danger.  The  storm  is  dissipated,  but  it  may  gather 
again  in  an  instant ;  the  friendly  hand  traces  out  a  line 
of  conduct ;  rules  of  prudence  point  out  the  necessity  of 
preparing  a  retreat.  Nor  will  it  leave  the  work  un- 
finished, but  will  again  take  up  the  pen  if  the  danger 
reappears. 

The  anonymous  writer.  Gentlemen,  was  Carnot ;  the 
geometer  whom  he  thus  preserved  to  science,  and  to  our 
affections,  was  M.  de  Prony.  At  that  epoch  Prony  and 
Carnot  had  never  seen  each  othei% 


44  CARNOT. 

The  years  1793  and  179i  were  characterized  by  two 
sorts  of  terror :  the  terror  of  the  interior,  I  have  just 
proved,  Gentlemen,  our  colleague  was  always  a  stranger 
to,  as  to  any  thing  criminal  in  it ;  but  the  terror  which 
the  French  soldiers  inspired  in  the  innumerable  enemies 
that  came  from  every  part  of  Europe  to  assail  our  fron- 
tiers,— this  sort  of  terror  was  indeed  the  work  of  Carnot ; 
it  was  glorious ;  the  recollection  of  it  wiU  be  immortal ; 
I  claim  it  for  the  memory  of  our  colleague  ;  I  claim  it 
also  for  the  honour  of  the  Academy.  You  will  not  re- 
fuse. Gentlemen,  again  to  follow  Carnot  in  this  fine  and 
brilliant  phase  of  his  public  career.  I  am  assured  in 
this  hope  by  your  devotion  to  our  country. 

CARNOT     ENTRUSTED    WITH    THE     ORGANIZATION     AND 
DIRECTION    OP    OUR    ARMIES. 

At  divers  epochs,  in  France  as  well  as  in  other  coun- 
tries, simple  administrators  have  been  seen  successfully 
to  occupy  the  eminent  positions  of  Minister  of  War,  and 
Minister  of  Marine.  The  Genei'al-in-chief,  the  Admiral, 
was  then  entrusted  with  a  command,  with  carte  blanche 
as  to  the  operations,  and  the  ministers  had  nothing  far- 
ther to  do  than  to  send  regular  and  opportune  provisions 
and  reinforcements.  Would  you  believe  it,  Gentlemen  ? 
it  was  in  this  confined  circle  that  bad  faith  and  envy 
wished  to  confine  the  decisive  influence  that  Cai'not  ex- 
ercised on  our  destinies.  But  it  will  be  easy  for  us  in  a 
few  words  to  tear  to  pieces  this  web  of  hideous  ingrati- 
tude. 

When  our  colleague  became,  in  August  1793,  member 
of  the  Committee  of  Public  Safety,  France  was  passing 
through  a  frightful  crisis.  The  wreck  of  Dumouriez's 
army  was  repulsed  from  one  position  to  another  ;  Valen- 


COMMANDER-IN-CHIEF.  45 

ciennes,  Conde,  opened  tlieir  gates  to  the  enemy ;  May- 
ence,  pressed  by  famine,  and  without  the  hope  of  relief, 
capitulated ;  two  Spanish  armies  invaded  our  territory ; 
20,000  Piedraontese  were  crossing  the  Alps ;  the  40,000 
Vendeans  of  Cathelineau  were  taking  Bressuire,  Thouars, 
Saumur,  Angers ;  they  menaced  Tours,  le  Mans,  and 
attacked  Nantes  on  the  right  bank  of  the  Loire,  whilst 
Charette  manoeuvred  on  the  opposite  bank  ;  Toulon  re- 
ceived an  English  fleet  into  its  port ;  in  a  word,  our 
principal  cities,  Marseilles,  Caen,  Lyons,  separated  them- 
selves violently  from  the  central  government. 

You  have  now  before  your  eyes,  CTcntlemen,  a  faint 
image  of  the  dangers  which  menaced  our  country ;  and 
have  some  people  dared  to  pretend  that  the  Convention, 
that  the  terrible  Convention,  hoped  to  escape  from  the 
imminent  catastrophe  that  almost  all  Europe  thought 
inevitable,  without  even  establishing  a  certain  connec- 
tion in  the  operations  of  its  generals  ?  and  can  it  have 
been  imagined  that,  in  entrusting  one  of  its  members 
with  the  almost  sovereign  direction  of  its  military  affairs, 
it  expected  from  him  only  the  methodical  measures  and 
regulations  compassed  by  a  purveyor  or  intendant  of  an 
army  ?  No,  no !  no  one  could  possibly  in  good  faith 
adopt  such  ideas. 

Do  not,  however,  believe  that  I  undervalue  Carnot's 
administrative  services.  I  admire,  on  the  contrary,  their 
noble  simplicity.  There  was  not,  assuredly,  at  that  time 
in  his  administration,  either  that  inextricable  series  of 
scribbling  which  the  smallest  affair  entails  on  us  in  the 
present  day  ;  nor  that  artistic  network  entangling  every 
one,  from  the  junior  clerk  of  the  ofRce  up  to  the  head  of 
the  department,  in  so  intricate  a  manner,  that  the  firmest 
and  boldest  hand  could  not  hope  to  break  a  link  or  sep- 


46  CARNOT. 

arate  the  elements.  The  chief  used  then  to  take  a 
responsible,  personal,  and  direct  cognizance  of  the  dis- 
patches that  were  addressed  to  him  ;  the  conceptions  of 
the  chosen  man  were  not  then  exposed  to  perish  under 
the  blows  of  an  envious  multitude  of  poor  intellects ;  a 
mere  sergeant  of  infantry,  then,  (young  Hoche)  did  not 
work  only  on  the  dusty  papers  in  the  archives,  when  he 
composed  A  Memoir  on  the  Means  of  penetrating  into 
Belgium  ;  tlien,  the  perusal  of  this  work  drew  from  Car- 
not  this  prophetic  exclamation  :  "  That  is  a  sergeant  of 
infantry  who  will  make  his  way."  Then  this  sergeant, 
watched  by  the  eye  in  all  his  actions,  became,  in  the 
space  of  a  few  months,  captain,  colonel,  brigadier-general, 
general  of  division,  and  general  in  chief ;  it  was  not  then 
only  a  small  class  that  was  invested  with  the  privilege 
of  furnishing  the  chiefs  of  our  armies ;  then,  both  in  fact 
and  by  right,  each  soldier  had  promotions  in  his  cartridge- 
box  :  splendid  actions  brought  them  out ;  yet  the  military 
force  then,  notwithstanding  the  important  services  that 
it  rendered  to  the  country,  notwithstanding  the  disorders 
of  that  epoch,  respectfully  lowered  its  fasces  before  the 
civil  authority,  the  proxy  of  the  nation. 

Let  us  cast  a  glance  towards  another  phase  of  the 
military  administration,  and  Carnot  will  not  appear  to  us 
either  less  great  or  less  successful. 

There  was  a  want  of  pure  copper ;  at  the  cry  of  the 
distressed  nation,  science  discovered  in  the  bells  of  the 
convents,  of  the  churches,  of  the  public  clocks,  an  inex- 
haustible mine,  whence  she  might  extract,  without  delay, 
all  the  metal  that  England,  Sweden,  and  Russia  refused 
her.  There  was  no  saltpetre  ;  some  lands,  where  for- 
merly only  enough  of  this  substance  would  have  been 
sought  to  add  certainty  to  some  delicate  chemical  analy- 


ARMY    REQUIRKMENTS    SUPPLIED.  47 

sis,  furnish  enough  for  all  the  requirements  of  our  armies 
and  our  fleets.  The  preparation  of  shoe-leather  used  to 
require  whole  months  of  labour ;  such  long  delays  did 
not  suit  the  wants  of  our  soldiers,  and  consequently  the 
tanner's  art  received  unhoped-for  improvements ;  days 
will  now  take  the  place  of  months.  The  manufacture  of 
arms  is  so  minute,  that  its  slowness  seems  inevitable ; 
but  immediately  some  mechanical  aids  are  brought  into 
action  to  strengthen,  to  direct,  to  take  the  place  of  the 
workman ;  the  products  increase  in  proportion  to  the 
demand  for  them.  Until  the  year  1794,  balloons  had 
been  only  a  mere  object  of  curiosity  ;  but  at  the  battle  of 
Fleurus,  a  balloon  carries  General  Morlot  into  the  region 
of  the  clouds ;  from  thence  the  smallest  manoeuvres  of 
the  enemy  are  perceived,  are  signalized  instantly,  and 
this  invention  of  purely  French  origin  procures  a  splen- 
did triumph  for  our  army.  Graphite  pencils  (black 
lead)  are  the  pen  and  ink  of  an  officer  on  a  campaign  ; 
it  is  with  the  pencil  that  he  Avrites  a  few  words  on  the 
pummel  of  his  saddle,  which  send  thousands  of  infantry, 
of  cavalry,  of  artilleiy-men  into  the  thickest  of  the  fight ; 
graphite  is  one  of  the  substances  that  Nature  seems  to 
have  denied  to  our  soil ;  the  Committee  of  Public  Safety 
orders  it  to  be  created  of  all  sizes,  and  this  order  to  make 
a  discovery  is  executed  without  delay ;  thus  the  country 
is  enriched  with  a  new  branch  of  industry.  To  be  brief, 
for  I  must  resign  myself  to  not  saying  every  thing,  the 
first  ideas  of  the  telegraph  are  drawn  from  some  folio 
books,  wherein  they  had  lain  useless  for  ages  ;  they  are 
perfected,  they  are  extended,  they  are  applied,  and  from 
that  moment  the  armies  receive  their  orders  in  a  few 
minutes  ;  the  Committee  of  Public  Safety  in  Paris  is 
enabled  to  follow  all  the  events  of  the  war,  to  the  east. 


48  CARNOT. 

the  north,  the  west,  as  if  it  were  seated  in  the  midst  of 
the  combatants. 

These  somewhat  spontaneous  creations,  these  patriotic 
directions  given  to  so  many  noble  intellects,  this  art,  now 
lost,  of  exciting  genius,  of  dragging  it  from  its  habitual 
indolence,  will  always  occupy  a  large  place  in  the  annals 
of  the  Committee  of  Public  Safety,  and  in  the  history  of 
our  colleague's  life.  Without  departing,  moreover,  from 
the  subject  that  now  occupies  us,  we  might  still  register 
many  other  services. 

Cai'not  was  one  of  that  very  small  number  of  men 
who,  in  1793,  firmly  believed  that  the  Republic  would 
sooner  or  later  triumph  over  its  innumerable  enemies. 
Thus,  although  he  gave  to  the  present  as  large  a  portion 
of  attention  as  circumstances  demanded,  yet  having  an 
eye  to  the  future  in  his  administration,  he  enriched  France 
with  many  great  institutions,  the  happy  effects  of  which 
can  only  be  slowly  developed. 

If  time  allowed  me,  I  should  have  to  cite  amongst  the 
great  establishments  towards  the  formation  of  which 
Carnot  contributed,  the  first  Normal  School,  the  Poly- 
technic School,  the  Museum  of  Natural  History,  the 
Conservatory  of  Arts  and  Trades ;  and  amongst  the 
labours  that  he  encouraged  by  his  suffrage,  was  the 
measurement  of  the  earth,  the  establishment  of  the  new 
system  of  weights  and  measures,  and  the  great,  the 
incomparable  statistic  tables. 

These  are  noble  titles,  Gentlemen,  for  an  era  of  de- 
struction. 

The  Convention  put  into  the  hands  of  Carnot  the 
colossal,  but  incoherent  mass  of  the  requisition.  It  was 
requisite  to  organize  it,  to  discipline  it,  to  instruct  it ; 
Carnot  produced  from  it  fourteen  armies.     It  was  also 


FOUNDS    PUBLIC    SCHOOLS.  49 

requisite  to  create  for  it  some  able  chiefs  :  our  colleao'ue 
knew,  with  a  certain  Athenian  general,  that  an  army  of 
Deer  commanded  by  a  Lion,  would  he  worth  more  than 
an  army  of  Lions  commanded  hy  a  Deer.  Carnot  duo- 
without  intermission  in  the  fruitful  and  inexhaustible 
mine  of  junior  officers  ;  as  I  before  said,  his  penetrat- 
ing eye  sought  in  the  most  obscure  ranks  for  talent 
united  with  courage,  with  disinterestedness,  and  elevated 
it  rapidly  to  the  highest  grades.  It  was  necessary  to 
coordinate  so  many  various  movements  !  Carnot,  like 
Atlas  in  the  fable,  carried  alone,  during  several  years 
the  -weight  of  all  the  military  events  in  Europe  ;  he 
wrote  with  his  own  hand  to  the  generals ;  he  gave  them 
detailed  orders,  wherein  all  the  eventualities  were  mi- 
nutely foreseen  ;  his  plans,  the  one  that  he  addressed  to 
Pichegru,  for  instance,  on  the  21  Ventose,  year  II., 
seemed  the  result  of  real  divination.  Facts  occurred 
so  entirely  justifying  the  forethought  of  our  colleao^ue, 
that  to  write  an  account  of  the  memorable  campaign  of 
1794,  there  -would  be  scarcely  a  few. proper  names  of 
villages  to  be  altered  in  the  instructions  that  he  addressed 
to  the  commander-in-chief  The  places  where  attacks 
were  to  be  made,  those  Avhere  they  M'ere  to  limit  tliera- 
selves  to  demonstrations,  to  skirmishes  ;  the  strength  of 
each  garrison,  of  each  post,  all  is  indicated,  all  is  regu- 
lated with  admirable  jirecision.  It  was  by  orders  from 
Carnot  that  Hoche  one  day  disappeared  from  before  the 
Prussian  army,  traversed  the  Vosges,  and,  uniting  him- 
self to  the  army  of  the  Rhine,  went  to  strike  a  decisive 
blow  on  Wurmsur,  which  occasioned  the  deliverance  of 
Alsace. 

In  1793,  while  the  enemy  was  expecting,  according  to 
the  classic  principles  of  strategy,  to  see  our  troops  ad- 


50  CARNOT. 

vanee  from  the  Moselle  to  the  Rhine  ;  whilst  he  was 
accumulating  formidable  means  of  resistance  on  the  lat- 
ter river,  Carnot,  without  troubling  himself  about  old 
theories,  detached  unawares  40,000  men  from  the  army 
of  the  Moselle,  and  sent  them  to  the  Meuse  by  forced 
marches.  Such  was  the  celebrated  manoeuvre  which 
decided  the  success  of  the  campaign  of  1793,  during  which 
the  Austrian  and  Dutch  generals  had  the  double  chagrin 
of  being  constantly  beaten,  and  this  against  all  rules.  Yes, 
Gentlemen,  the  national  tribune  was  but  just,  on  the  day 
when  it  echoed  these  noble  words,  which  have  now 
become  historical :    "  Carnot  has  organized  victory" 

CARNOT    ON    THE    FIELD    OF    BATTLE     AT    "WATTIGNIES. 

It  might  be  said  of  the  French  armies,  as  of  certain 
painters,  that  they  have  had  various  styles.  On  the  day 
of  battle,  it  is  true,  the  imperial  armies  and  the  repub- 
lican armies  precipitated  themselves  on  the  enemy  with 
the  same  intrepidity  ;  with  this  exception  all  else  was 
different.  The  imperial  soldier  saw  his  country  only  in 
the  ARMY  ;  it  was  for  the  honour,  for  the  glory  of  the 
army,  that  he  shed  his  blood  at  Wagram,  at  Sommo- 
Sierra,  at  the  Moscowa.  The  republican  soldier  fought 
for  his  COUNTRY ;  the  national  independence  was  the 
thought  that,  above  all  others,  animated  him  in  the  com- 
bat ;  as  to  recompenses,  he  did  not  even  dream  of  them. 

Follow  those  same  soldiers  into  [jrivate  life,  and  you  will 
see  this  dissimilitude  continue.  The  imperialist  remains 
a  soldier  both  in  his  sentiments  and  in  his  manners  ;  the 
republican,  confounded  in  the  mass  of  the  population, 
becomes  soon  undistingui.-hable  from  an  artisan,  from  a 
labourer,  Avho  bad  never  quitted  his  workshop  or  his 
plough. 


BATTLE    OF    WATTIGNIES.  51 

It  is  these  shades,  cleverly  seized,  artistically  repro- 
duced, that  from  the  first  day  struck  the  public  with  such 
a  lively  admiration  for  the  productions  of  David.  One 
day,  an  officer  of  the  Empire,  known  for  his  brilliant 
valour,  said  to  me  in  the  library  of  the  Institute,  "  I 
cannot  reconcile  myself  to  seeing  General  Carnot  in  a 
man  dressed  in  short  h~eeches  and  blue  stockhigs."  I 
took  the  opposite  view ;  upon  which  he  added,  "  Well, 
be  it  so  !  blue  stockings  may  suit  a  general  who  was 
never  baptized  by  fire ! "  Yesterday,  also,  with  less 
roughness  it  is  true,  in  word,  one  of  our  co-academicians 
reproduced  in  my  presence  the  same  thought.  I  shall 
then  fulfil  a  duty  by  proving  that,  when  occasion  required, 
the  man  in  blue  stockings  knew  well  how  to  risk  his  life. 

The  Prince  of  Cobourg,  at  the  head  of  sixty  thousand 
men,  occupied  all  the  outlets  of  the  forest  of  Mormale, 
and  blockaded  ISIaubeuge.  This  town  once  taken,  the 
Austrians  would  have  met  with  no  more  serious  obstacles 
to  their  reaching  Paris.  Carnot  perceives  the  danger ; 
he  persuades  his  colleagues  in  the  Committee  of  Public 
Safety  that  our  army,  notwithstanding  its  numerical  infe- 
riority, can  give  battle  ;  that  it  must  attack  the  enemy  in 
its  apparently  impregnable  positions.  It  was  one  of  those 
critical  moments  that  decide  the  fate,  the  existence  of 
nations.  General  Jourdan  hesitates  under  such  a  terrible 
responsibility.  Carnot  goes  to  the  army ;  in  a  few  hours 
all  is  ari-anged,  all  is  agreed  upon  ;  the  troops  open  out, 
they  fall  upon  their  enemies  ;  but  the  latter  are  so  numer- 
ous, they  occupy  so  well  chosen  a  position,  they  have  dug 
so  many  entrenchments,  they  have  furnished  them  so  for- 
midably with  artillery,  that  success  is  uncertain.  At  the 
close  of  the  day,  our  right  wing  had  gained  some  ground  ; 
but  the  lett  wing  had  perhaps  lost  more.     It  had  more- 


52  CARNOT. 

over  left  some  guns  in  possession  of  the  Austrians.  Let 
us  strengthen  the  left  wing,  exclaimed  the  old  tacticians. 
No,  no,  replied  Carnot ;  what  signifies  by  which  wing  Ave 
triumph.  It  w^as  necessary,  with  good  will  or  ill  will,  to 
yield  to  the  authority  of  the  people's  representative  !  The 
night  is  employed  in  breaking  up  the  wing  already  com- 
promised ;  its  principal  troops  are  marched  to  the  right, 
and  when  the  sun  rose,  it  was  in  some  measure  a  new 
army  that  Cobourg  found  opposed  to  him.  The  battle 
recommenced  with  fresh  fury.  Shut  up  in  their  redoubts, 
protected  by  woods,  by  palisades,  by  quickset  hedges,  the 
Austrians  resist  valiantly ;  one  of  our  attacking  columns 
is  repulsed,  and  begins  to  disperse  !  Oh  !  who  could  de- 
scribe the  cruel  anguish  that  Carnot  experienced.  Doubt- 
less his  imagination  already  represents  to  him  the  enemy 
penetrating  into  the  capital,  defiling  along  the  boulevards, 
and  abandoning  themselves  to  those  acts  of  Vandalism, 
with  which  in  so  many  proclamations,  in  so  many  insolent 
manifestoes,  we  had  been  threatened  !  These  distracting 
thoughts,  however,  do  not  abate  his  courage  :  Carnot 
rallies  his  soldiers,  reforms  them  on  a  plot  of  ground  ; 
solemnly,  before  the  whole  army,  degrades  the  general 
who,  in  disobeying  positive  orders,  had  allowed  himself 
to  be  defeated  ;  seizes  the  musket  of  a  grenadier,  and 
marches  at  the  head  of  the  column,  in  the  civil  costume 
of  the  representative  of  the  nation.  Nothing  could  now 
withstand  the  impetuosity  of  our  troops  ;  the  charges  of 
the  Austrian  cavalry  are  repelled  with  the  bayonet ;  all 
who  enter  into  the  excavated  roads  around  Wattignies  ai'e 
sure  to  meet  with  death.  Carnot  finally  penetrated  into 
the  village,  the  very  key  of  the  position  of  the  enemy's 
army,  over  heaps  of  dead  bodies,  and  from  that  moment 
the  sieee  of  Maubeu";e  was  at  an  end. 


BATTLE    OF    WATTIGNIES.  63 

It  will  be  asked,  no  doubt,  where  Carnot  had  gained 
this  firmness,  this  vigour,  the  military  coup  d'oeil,  that 
knowledge  of  troops  ?  Seek  not  for  the  source  but  in  his 
ardent  patriotism.  It  was  at  Wattignies  that  for  the  first 
time  he  heard  the  musketiy  and  cannon  of  the  enemy. 
But  I  am  mistaken,  Gentlemen  ;  it  is  the  second,  and  not 
the  first  time :  the  first  time,  Carnot,  marching  as  at  Wat- 
tignies, musket  in  hand,  at  the  head  of  a  new  levy  of  sol- 
diers, carried  the  town  of  Furnez  by  assault,  then  occupied 
by  the  English. 

The  battle  of  Wattignies,  considered  as  to  its  results, 
will  always  occupy  one  of  the  foremost  places  in  the 
annals  of  the  French  Revolution.  I  should  probably  be 
less  positive  on  the  difficulties  of  that  day,  compared 
with  so  many  others,  if  I  could  not  support  myself  by 
the  opinion  of  the  Prince  of  Cobourg  himself  When  he 
saw  the  French  battalions  begin  to  break,  that  general 
could  not  find  terms  too  strong  to  express,  in  presence  of 
bis  staff,  the  confidence  that  he  felt  in  the  number  and 
ardour  of  his  troops,  and  in  the  obstacles  of  all  sorts,  both 
natural  and  artificial,  that  the  uneven  ground  occupied  by 
the  Austrians  presented  to  the  assailants.  He  exclaimed  : 
"  The  Republicans  are  excellent  soldiers ;  but  if  they  dis- 
lodge me  from  this  position,  I  will  consent  to  become  a 
Republican  myself."  Certainly  nothing  more  decided  or 
more  energetic  could  issue  from  the  mouth  of  Cobourg. 
For  ray  part,  I  could  not  conceive  a  more  glorious  bulletin 
of  the  battle  of  Wattignies  ! 

The  German  author  from  whom  I  have  borrowed  this 
anecdote  does  not  say  whether,  after  having  dislodged  him, 
the  French  summoned  the  Austrian  general  to  keep  his 
word.  I  have  some  reason  to  suppose  that,  notwithstand- 
ing their  spirit  of  propaganda,  they  disdained  a  recruit 


54  CARXOT. 

who  would  have  submitted,  but  whose  vocation  seemed 
very  uncertain. 

STATISTICS    OP    THE    OPERATIONS    OF    THE    ARMIES. 

Carnot  felt  the  propriety,  the  want,  of  showing  towards 
the  national  armies  a  deference  from  which  absolute  gov- 
ernments formerly  felt  themselves  free,  whilst  their  sol- 
diers were  enrolled  at  a  money  price  :  each  year  he  had 
to  unroll  to  the  eyes  of  the  nation  a  detailed  table  of  the 
battles  given  by  our  legions,  and  of  the  effects  that  had 
thence  resulted.  Here  follows  the  conclusion  of  the  reci- 
tal of  the  campaign  of  seventeen  months,  during  which 
the  troops  of  the  Republic  never  laid  down  their  arms  for 
a  single  day. 

Twenty-seven  victories,  eight  of  which  were  pitched 
battles  ;  120  combats  of  minor  importance  ;  80,000  ene- 
mies killed;  91,000  pi-isoners ;  116  fortresses  or  strong 
towns  taken,  36  of  which  had  required  to  be  besieged  or 
blockaded  ;  230  forts  or  redoubts  taken  ;  3,800  guns  of 
various  sizes  ;  70,000  muskets  ;  1,900  milHers  (tons)  of 
gunpowder ;  90  flags.  Let  people,  if  they  dare,  after 
reading  this  table,  say  that  statistics  are  not  eloquent ! 

CARNOT,  NAMED  BY  FOURTEEN  DEPARTMENTS,  ENTERS 
THE  COUNCIL  OF  THE  ELDERS,  AND  THEN  THE  EXEC- 
UTIVE   DIRECTORY. HOCHE    SENT    TO    LA    VENDEE, 

MOREAU    AND    JOURDAN    TO    THE    RHINE,  AND    BONA- 
PARTE   TO    ITALY. 

Carnot  quitted  the  Council  of  Public  Safety  shortly 
before  the  insurrection  of  the  Parisian  sections  against 
the  Convention.  Carry  back  your  recollection  towards 
the  military  events  that  followed  the  forced,  though  legal 
reti'eat  of  our  colleague,  and  you  will  see  almost  every- 


COUNCIL  OF  THE  ELDERS.  55 

where  that  victory  abanJoned  the  standards  of  the  Repub- 
lic, and  reverses  succeeded  each  other,  as  triumphs  did 
before  ;  all  the  springs  were  unbent,  mistrust  and  dis- 
couragement took  possession  of  every  mind  ;  and  you 
will  then  understand,  better  than  by  an  uninterrupted 
series  'of  brilHant  successes,  of  wliat  importance  the 
genius  of  one  man  alone  may  be  to  the  destiny  of  na- 
tions. 

Carnot  was  called  to  the  legislature  which  succeeded 
to  the  National  Convention  by  fourteen  departments.  If 
I  were  allowed  to  express  a  personal  sentiment,  I  would 
say  how  pleased  I  have  been  to  find  the  name  of  the  de- 
partment of  the  Eastern  Pyrenees,  in  the  list  of  those 
which  tried  to  reward  our  great  citizen  for  the  outrages 
that  a  handful  of  members,  excited  by  the  butcher  Le- 
gendre,  cast  upon  him  on  several  occasions.  A  short 
time  after  he  entered  the  Council  of  the  Elders,  Carnot, 
on  the  refusal  of  Sieyes,  became  one  of  the  five  members 
of  the  Executive  Directory. 

At  the  moment  when  he  for  the  second  time  was  thus 
called  to  direct  our  armies,  the  Republic  had  reached  the 
verge  of  an  abyss.  The  public  treasury  was  empty.  The 
Directory  had  great  trouble  even  in  procuring  clerks  and 
servants  in  their  office,  so  much  was  it  thought  to  be  in- 
solvent. The  despatching  of  a  courier  was  often  delayed 
on  account  of  the  impossibility  of  providing  for  the  ex- 
penses of  the  journey ;  the  generals  themselves  no  longer 
received  the  eujld  francs  (I  am  not  mistaken),  the 
eight  francs  ])er  month  "en  numeraire,"  (in  cash,)  that 
had  been  granted  to  them,  as  a  supplement  to  their  pay 
in  assignats  ;  the  agricultural  producers  no  longer  sup- 
plied the  markets ;  the  manufacturers  refused  to  sell  their 
products,  because  there  was  a  right  to  pay  for  them  in 


56  CARNOT. 

paper-money,  and  paper-money  then  was  of  no  value. 
From  one  end  of  France  to  the  other,  famine  had  thrown 
people  into  an  extreme  state  of  irritation,  which  daily 
manifested  itself  in  sanguinary  disorders.  The  army 
offered  a  no  less  deplorable  aspect :  it  was  deficient  in 
means  of  transport,  in  clothing,  in  shoes,  in  munitions. 
Misery  had  engendered  a  want  of  discipline.  Pichegru 
was  weaving  criminal  relations  with  the  Prince  of  Conde, 
allowed  himself  to  be  beaten  at  Heidelberg,  compromised 
the  array  of  Jourdan,  evacuated  Mannheim,  raised  the 
siege  of  Mayence,  and  ceded  the  frontier  of  the  Rhine 
to  the  Austrians.  War  recommenced  in  La  Vendee  ; 
the  English  threatened  us  with  a  descent  in  the  Pays- 
Bas,  and  on  our  own  coasts.  In  a  word,  on  our  Alpine 
frontier,  Scherer  and  Kellermann  painfully  sustained  a 
defensive  war  against  the  united  forces  of  the  Emperor  of 
Austria,  the  King  of  Sardinia,  and  the  confederated 
Italian  princes. 

Gentlemen,  the  great  strength  of  mind,  united  to  the 
most  ardent  patriotism,  was  requisite,  under  such  cruel 
circumstances,  to  induce  men  to  accept  the  burden  of 
public  affairs.  Let  us  add  that  Carnot  was  so  little  blind 
to  the  faults  of  the  Constitution  of  the  year  IIL,  and, 
above  all,  to  the  inconveniences  of  a  multiple  executive 
power,  that  he  had  publicly  pointed  them  out  in  the 
midst  of  the  Convention,  at  the  time  when  this  constitu- 
tion was  discussed.  He  then  exclaimed  :  "  The  destinies 
of  the  state  will  henceforward  depend  only  on  the  personal 
character  of  five  men.  The  more  these  characters  differ, 
the  more  dissimilar  will  be  the  views  of  these  five  direc- 
tors, and  the  more  will  the  state  have  to  suffer  from  their 
alternate  influence."  The  majority  disdained  tliese  just 
apprehensions  ;  faithful  to  a  line  of  conduct  from  which 


BONAPARTE    IN    ITALY.  57 

he  was  never  seen  to  swerve,  Carnot  submitted  without  a 
murmur  ;  and,  as  soon  as  the  new  government  had  re- 
ceived the  legal  sanction,  he  served  it  with  the  same 
energy,  zeal,  and  devotion  that  he  had  before  displayed 
as  a  member  of  the  Committee  of  Public  Safety. 

La  V  endee  was  on  fire  ;  Iloche  receives  orders  from 
Carnot  to  pacify  it,  together  with  a  new  system  of  opera- 
tions. This  republican  general  complies,  triumphs  over 
Charette,  takes  possession  of  Stofflet,  and  clears  the  Moi*- 
bihan  of  the  numerous  bands  of  chouans  who  ravaged  it. 
In  less  than  eight  months,  the  civil  war,  that  impious 
war,  in  which,  however,  great  courage  was  displayed  on 
both  sides,  ceased  to  desolate  our  territory. 

On  the  Rhine,  our  armies  are  placed  under  the  com- 
mand of  Jourdan  and  Moreau.  A  scientific  and  pro- 
found plan  of  the  campaign  connected  the  movements  of 
those  two  generals,  and  soon  carried  their  victorious 
troops  into  the  heart  of  Germany. 

In  La  Vendee,  in  Germany,  on  the  Rhine,  Carnot,  as 
we  have  shown,  had  infused  confidence  into  officers 
already  celebrated  by  memorable  triumphs.  The  com- 
mand of  the  army  of  Italy  he  gave,  on  the  contrary,  to  a 
general  only  twenty-five  years  of  age,  whose  known 
claims  were  then  restricted  to  some  secondary  services 
that  he  achieved  during  the  siege  of  Toulon,  and  to  the 
easy  defeat  of  the  Parisian  Sectionaries,  on  the  13th 
Vendumiaire,  year  III.,  on  the  humble  fields  of  battle  of 
the  Pont  Royal  and  the  Rue  St.-IIonore,  and  the  steps 
of  St.-Roch.  I  here  claim  for  Carnot  the  honour  of 
having  personally  pointed  out  and  selected  the  young 
Genei-al  Bonaparte  for  the  command  of  our  third  army, 
because  it  legitimately  belongs  to  him ;  because  this 
choice  was  long  unjustly  considered  as  the  result  of  a 
3  * 


58  CARNOT. 

boudoir  intrigue ;  and  because  every  one,  I  think,  must 
be  glad  to  see  the  liistory  of  the  incomparable  campaign 
of  Italy  purified  from  such  a  stain.  I  have  thought,  in 
short,  that  I  ought  not  to  neglect  to  show  you  your  col- 
league discerning  with  infinite  perspicacity  the  hero  of 
Eivoli,  of  Arcole,  of  Castiglione,  through  the  bark  of 
timidity,  of  reserve, — let  us  out  with  the  true  word,  of 
awkwardness, — that  everybody  then  remarked  in  the 
protege  of  Barras. 

I  foresee  all  the  incredulity  I  should  meet  with,  if  I 
were  to  venture  on  still  farther  extending  the  limits  of 
the  influence  that  our  colleague  exercised  over  the  Italian 
campaign  ;  and  yet,  should  I  not  have  found,  even  in  the 
small  number  of  official  documents  already  known  to  the 
public,  under  date  of  the  10th  Floreal,  year  IV.,  for 
example,  a  despatch  from  the  head-quarters  of  Cherasco, 
in  which  Bonaparte  writes  to  Carnot : — "  The  armistice 
concluded  between  the  King  of  Sardinia  and  ourselves, 
enables  me  to  communicate  through  Turin,  that  is  to  say, 
to  spare  half  the  journey ;  /  could  therefore  quickly  re- 
ceive YOUR  ORDERS  AND  LEARN  YOUR  INTENTIONS,  AS 
TO    THE    DIRECTION    TO    BE    GIVEN    TO    THE  ARMY."      A 

letter  to  the  Minister  of  Finance,  of  the  2d  Prairial,  year 
IV.,  dated  from  head-quarters  at  Milan,  would  afibrd  the 
following  sentence  : — "  The  Executive  Dii-ectory,  who 
named  me  to  the  command  of  this  army,  has  arranged 
A  PLAN  OF  offensive  WARFARE  which  requires  prompt 
measures  and  extraordinary  I'esources." 

The  2d  of  Prairial,  year  IV.  (May  21,  1796,)  Carnot 
wrote  thus  to  the  young  general: — "Attack  Beaulieu 
before  reinforcements  can  reach  liira ;  do  not  neglect 
any  thing  to  prevent  this  junction  ;  you  must  not  weaken 
yourself  before  him,  and  above  all,  do  not,  by  disastrously 


BONAPARTE    IN    ITALY.  59 

dividing  your  force,  give  him  the  means  of  beating  us  in 
detail,  and  retaking  the  ground  he  has  lost.  After  the 
defeat   of  Beaulieu,  you   will  make   the   expedition   to 

Leghorn The  intention  of  the  Directory  is,  that 

the  army  shall  not  pass  beyond  the  Tyrol,  until  after  the 
expedition  to  the  south  of  Italy." 

Doubtless,  these  general  orders  are  not  the  campaign 
of  Italy.  No  human  intelligence  could  foresee  either  the 
route  that  General  Beaulieu  would  follow  after  his  sep- 
aration from  the  Piedmontese  army,  nor  the  manoeuvres 
of  "Wurmsur,  nor  the  long  resistance  made  at  Mantua  by 
that  old  general,  nor  the  marches  of  Alvinzi,  nor  many 
glorious  incidents  which  I  abstain  from  recalling ;  with- 
out doubt  it  required  all  the  hardihood  and  genius  of 
Bonaparte,  and  the  cooperation  of  such  officers  as  Mas- 
sena,  Augereau,  Lannes,  Murat,  Rampon,  to  annihilate 
in  a  few  months  three  large  Austrian  armies.  Finally, 
all  that  I  have  wished  to  say  is,  that  it  would  be  unjust 
to  entirely  omit  the  name  of  Carnot  in  reciting  those 
immortal  campaigns. 

I  should  have  a  right  to  say  even  more  were  we  study- 
ing another  phase  of  those  wars, — their  moral  and  civil- 
izing phase.  Who  does  not  remember  those  treaties  of 
peace,  in  which  masterpieces  of  painting  and  of  sculpture 
wei-e  inducements  to  pardon  perfidy  and  treachery  in  our 
enemies,  and  the  official  visits  of  our  victorious  generals 
to  diffident  learned  men,  rendered  illustrious  by  important 
discoveries  ?  Well,  Gentlemen,  all  this,  whatever  peo- 
ple may  say  of  it,  was  prescribed  by  Carnot.  Will  any 
doubts  still  be  entertained  if  I  transcribe  the  following 
letter  from  our  colleague,  dated 

"  24tli  of  Prairial,  year  IV. 

"  General,  in  recommending  you,  by  our  letter  of  the 


60  CAKNOT. 

26th  Floreal,  to  visit  and  receive  the  celebrated  artists 
of  the  countries  in  which  you  happen  to  be,  we  have 
especially  designated  the  great  astronomer  Oriani,  of 
Milan,  as  deserving  of  being  protected  and  honoured  by 
the  republican  troops.  The  Directory  will  learn  with 
satisfaction  that  you  have  fulfilled  its  intentions  respect- 
ing this  learned  and  distinguished  man,  and  it  requests 
you  consequently  to  relate  what  you  have  done  to  prove 
to  citizen  Oi'iani  the  interest  and  the  esteem  that  the 
French  have  always  felt  for  him,  and  to  testify  that  they 
know  how  to  unite  the  love  of  glory  and  liberty  with  a 
love  for  the  arts  and  for  talent." 

PUBLICATION  OF  THE  WORK  ENTITLED  "  REFLECTIONS 
ON  THE  METAPHYSICS  OF  THE  INFINITESIMAL  CAL- 
CULUS." 

The  word  science,  which  the  series  of  events  has  just 
brought  to  my  pen,  reminds  me  that  this  epoch  is  that  of 
the  publication  of  one  of  Carnot's  mathematical  works. 
I  am  aware  how  fatiguing  it  will  be  to  you  to  listen  to 
the  analysis  of  it ;  but  it  is  quite  necessary  that  the 
savant  also  should  be  occasionally  represented  in  this 
assembly.  The  early  and  very  remarkable  work  on 
machines  of  which  we  gave  an  idea,  has  sufficiently  in- 
dicated how  much  we  may  expect  from  the  firm,  lucid, 
and  penetrating  mind  of  Carnot.  It  was  then  a  brilliant 
and  glorious  future  which  the  young  officer  brought  as 
an  offei'ing  to  his  country,  when,  obeying  the  voice  of  his 
fellow-citizens,  he  exchanged  the  smooth,  tranquil  life  of 
the  mathematician,  for  the  adventurous  and  rock-bestrewn 
career  of  the  tribune.  This  sacrifice,  moreover,  he  did 
not  make  without  regret ;  for  geometry  was  always  his 
favourite  relaxation.     Debarred  by  imperious  daily  du- 


THE    INFINITESIMAL     CALCULUS.  61 

ties  from  the  pleasure  of  "  measuring  himself  with  "  the 
grand  problems  whose  solution  requires  years  of  con- 
tinuous and  persevering  effort,  Carnot  chose  those  diffi- 
cult but  circumscribed  questions  which  may  be  taken  up, 
abandoned,  and  taken  up  again,  by  fits  and  starts  ;  which 
an  elevated  mind  capable  of  coping  with  difficult  sub- 
jects, develops  and  fathoms  without  paper  or  pencil, 
either  during  a  walk,  in  the  midst  of  the  excitements  of 
a  crowd,  the  gayeties  of  a  l:)anquet,  or  the  vigils  of  labo- 
rious nights  ;  in  a  word,  he  directed  his  meditations  to- 
wards the  "  metaphysics  of  the  calculus."  In  the  present 
day  such  researches  would  be.  I  fear,  but  little  relished  ; 
nevertheless,  if  we  recur  to  the  times  when  mathematical 
studies  gradually  led  to  the  consideration  of  quantities  of 
such  diffiirent  natures,  we  shall  be  amply  aware  of  the 
apprehension  with  which  they  inspired  exact  philosophers, 
and  must  acknowledge  that,  on  many  points,  it  is  rather 
habit  than  true  science  which  has  rendered  us  more  con- 
fident. 

Amongst  the  quantities  to  which  I  have  alluded,  the 
"  eVra^tonaZ"  presented  themselves  first.  The  ancients 
scrupulously  avoided  using  them  ;  the  moderns  would 
also  have  wished  to  avoid  the  use  of  them  ;  "  but  they" 
(the  quantities)  " gained  the  day  hy  their  numbers"  says 
the  ingenious  author  of  the  "  Geometry  of  Infinites." 

To  the  quantities  which  were  not  numerically  assign- 
able, succeeded  the  impossible  quantities,  the  "  imaginary 
quantities"  regular  symbols  of  which  it  would  be  vain  to 
attempt  to  give,  not  only  the  exact  values,  but  even  mere 
approximations.  These  imaginaries  are  nevertheless  used 
in  combination  by  addition  and  subtraction ;  they  are 
multiplied  and  divided,  the  one  by  the  other  in  the  same 
manner  as  real  quantities ;  at  the  end  of  the  calculation 


62  CARNOT. 

the  imaginaries  sometimes  disappear  amongst  the  trans- 
formations which  they  undergo,  and  the  result  is  then 
held  to  be  quite  as  certain  as  if  it  had  been  arrived  at 
without  the  help  of  these  algebraic  hieroglyphics.  It 
must  be  confessed  that,  though  thousands  on  thousands 
of  applications  of  the  calculus  justify  this  confidence,  few 
geometers  fail  to  take  credit  to  themselves  for  the  ab- 
sence of  imaginary  quantities  in  the  demonstrations 
where  they  have  been  able  to  avoid  them. 

The  "  irifinite  "  first  made  its  irruption  into  geometry 
on  the  day  when  Archimedes  determined  the  approxi- 
mate proportion  of  the  diameter  to  the  circumference  by 
assimilating  the  circle  to  a  polygon  "  ^vith  an  infinite 
number  of  sides."  Bonaventura  Cavalieri  afterwards 
went  much  farther  in  the  same  field  of  research  ;  various 
considerations  led  him  to  distinguish  some  "  infinitely 
great  quantities  "  of  several  orders,  from  some  infinite 
quantities  which  were  nevertheless  infinitely  smaller  than 
other  quantities.  Can  we  be  astonished  that,  at  sight  of 
such  results,  and  notwithstanding  his  lively  predilection 
for  combinations,  which  had  led  hira  to  veritable  dis- 
coveries, the  ingenious  Italian  author  should  have  ex- 
claimed, in  the  style  of  that  period,  "  Here  are  difip^cidties 
of  which  even  the  arms  of  Achilles  coidd  make  nothing!" 

The  '■'■infinitely  small"  quantities  had,  for  their  part, 
slipped  into  geometry  even  before  the  "  infinitely  great" 
and  this  not  only  to  facilitate  or  abridge  such  and  such 
demonstrations,  but  as  the  immediate  and  necessary  re- 
sult of  certain  elementary  properties  of  curves. 

Let  us  examine,  in  effect,  the  properties  of  the  most 
simple  of  all — the  circumference  of  a  circle  ;  and  by  that 
we  will  not  understand  the  rugged  clumsy  curve  which 
we  should  succeed  in  drawing  by  the  aid  of  our  com- 


THE    DIFFERENTIAL    CALCULUS.  63 

passes  or  best  geometrical  drawing-pens  ;  but  really  the 
circumference  of  a  circle  endowed  with  an  ideal  per- 
fection, really  a  curve  without  thickness  and  without 
roughness  of  any  sort.  Let  us,  in  imagination,  draw  a 
tangent  to  this  curve.  At  the  point  where  the  tangent 
and  the  curve  touch  one  another,  tliey  will  form  an  angle, 
which  has  been  called  the  "  angle  of  contact."  This 
angle,  since  the  first  origin  of  mathematical  science,  has 
been  the  object  of  the  most  serious  reflections  of  geom- 
eters. Since  two  thousand  years  ago  it  has  been  rigor- 
ously demonstrated  that  no  straight  line,  drawn  from  the 
apex  of  the  angle  of  contact,  can  be  included  between  its 
two  sides,  and  that  it  cannot  pass  between  the  curve  and 
the  tangent.  Well,  I  ask,  what  else  is  that  angle  into 
which  an  infinitely  fine  straight  line  cannot  be  introduced 
or  insinuated,  but  an  infinitely  small  quantity. 

The  infinitely  small  angle  of  contact,  into  which  no 
straight  line  can  be  introduced,  may  nevertheless  include 
between  its  two  sides  milHons  of  circumferences  of  cir- 
cles, all  greater  than  the  first.  This  truth  is  established 
by  reasoning  of  an  incontestable  and  uncontested  force. 
Here,  then,  we  have,  in  the  very  heart  of  elementary 
geometry,  an  infinitely  small  quantity,  and,  what  is  still 
more  incomprehensible,  susceptible  of  being  divided  as 
much  as  we  please  !  The  human  intellect  was  humili- 
ated and  lost  in  face  of  such  results ;  but,  at  any  rate, 
these  were  results,  and  it  submitted. 

The  infinitely  small  quantities  which  Leibnitz  intro- 
duced into  his  differential  calculus  excited  moi*e  scruples. 
This  great  geometer  distinguished  several  orders  of  them, 
those  of  the  second  order  might  be  neglected  in  relation 
with  the  infinitely  small  of  the  first ;  these  infinitely 
small  of  the  first  order  in  their  turn  disappeared  before 


64  CARNOT. 

finite  quantities.  At  eacli  transformation  of  the  formulae 
it  miglit  be  possible,  according  to  this  hierarchy,  to  dis- 
embarrass one's  self  of  fresh  quantities  ;  and,  nevertheless, 
one  was  obliged  to  believe,  to  admit,  that  the  definitive 
results  were  i-igorously  exact ;  tliat  the  infinitesimal  cal- 
culus was  not  mei'ely  a  mere  method  of  approximation. 
Such  was,  considering  the  whole  thing,  the  origin  of  the 
strong  and  tenacious  opposition  which  the  new  calculus 
raised  up  at  its  birth  ;  such  was  also  the  difficulty  which 
a  man  equally  celebrated  as  a  geometer  and  a  theologian, 
Berkeley,  bishop  of  Cloyne,  had  in  view  when  he  ex- 
claimed, addressing  himself  to  the  incredulous  in  matters 
of  religion,  "  Look  at  the  science  of  mathematics  ;  does 
it  not  admit  mysteries  more  incomprehensible  than  those 
of  religion  ?  " 

Tiiese  mysteries  at  the  present  day,  exist  no  longer 
for  those  who  desire  to  become  initiated  in  the  knowl- 
edge of  the  methods  which  constitute  the  differential 
calculus  in  Newton's  theory  of  fluxions  ;  in  a  paper 
wherein  D'Alembert  introduces  the  consideration  of  the 
limits  towards  which  the  ratios  of  the  finite  differences 
of  functions  converge  ;  or,  indeed,  in  Lagrange's  Theory 
of  Analytical  Functions.  Nevertheless,  Leibnitz's  course 
has  prevailed,  because  it  is  more  simple,  easier  to  recol- 
lect, and  more  convenient  in  practice.  It  is,  then,  im- 
portant to  study  it  in  itself,  to  penetrate  into  its  essence, 
and  to  assure  one's  self  of  the  perfect  exactness  of  the 
rules  Avhich  it  furnishes,  without  the  necessity  of  cor- 
roborating them  by  the  results  of  the  calculus  of  fluxions, 
or  of  limits,  or  of  functions.  That  task, — I  mean  the 
search  for  the  true  spirit  of  differential  analysis, — forms 
the  principal  oI)ject  of  the  book  which  Carnot  published, 
in    1799,  under   the  modest   title   of  Rejlections   on   the 


EPOCH    OF    THE    REVOLUTION.  G5 

3Ietaphysics  of  the  Infinitesimal  Calculus.  I  am  bold 
enough  to  assert  that  the  authors,  otherwise  so  excellent, 
of  the  best  treatises  on  the  differential  calculus,  have  not 
sutlicieutly  consulted  the  work  of  our  colleague.  The 
advantages  which  ought  to  result  from  the  immediate  in- 
troduction of  infinitely  small  or  elementary  quantities 
into  formulas  ;  the  considerations  by  help  of  which  it  may 
be  proved  that  the  calculator,  by  afterwards  throwing 
aside  these  quantities,  will  arrive  nevertheless  at  mathe- 
matically exact  results,  by  means  of  certain  compensations 
for  errors  ;  in  a  word,  the  fundamental  and  characteristic 
traits  of  Leibnitz's  method,  are  analyzed  by  Cax'not,  with 
a  clearness,  a  certainty  of  judgment,  and  an  ingenuity, 
which  we  should  look  for  in  vain  elsewhere,  though  the 
question  has  been  the  object  of  the  reflections  and  re- 
searches of  the  greatest  geometers  of  Europe. 

CARNOT    BEING    "FRUCTIDORISE  "    IS    OBLIGED    TO    RE- 
CUR   TO    FLIGHT. HE     IS    ERASED    FROM    THE     LIST 

OF    THE    INSTITUTE,    AND     SUCCEEDED    BY    GENERAL 
BONAPARTE. 

France  has  always  shown  itself  an  idolater  of  military 
glory.  Satisfy  this  passion  largely  in  a  national  war,  and 
you  need  not  be  uneasy  about  the  administration  of  the 
interior,  however  imperfect  it  may  be.  The  sympathies 
of  the  people,  and  in  case  of  need  even  their  entire  sub- 
mission, may  be  gained  by  any  government  that  takes 
care  to  adorn  itself  monthly  with  a  new  victory  over  its 
external  enemies.  I  perceive  but  one  exception  to  this 
rule  in  our  annals.  It  is  also  requisite,  however,  that,  by 
an  assimilation,  too  often  deceitful,  the  legal  representa- 
tives of  the  country  should  be  considered  as  the  faithful 
interpreters  of  the  wishes,  the  sentiments,  the  opinions 


66  CARNOT. 

of  the  majority.  The  exception  to  Avhich  I  am  about 
to  allude,  will  be  furuii>hed  by  our  Directorial  govern- 
ment. 

When  the  elections  of  the  year  V.  brought  a  reinforce- 
ment of  royalists  to  the  two  minorities  of  the  Council 
of  Five-Hundred,  and  of  the  Elders,  who  till  then  had 
limited  themselves  to  making  a  very  moderate  opposition 
to  the  Directory ;  when,  strong  in  what  they  thought  the 
popular  support,  the  minority,  fancying  that  they  had  be- 
come the  majority,  took  off  the  mask  so  far  as  to  name 
for  the  presidency  of  the  Council  of  Five-Hundred  that 
same  Pichegru,  who  not  long  before  had  branded  with 
treason  the  laurels  that  he  had  gained  in  Holland  in  the 
name  of  the  Republic  ;  when  the  enemies  of  the  Direc- 
torial power  openly  unveiled  their  projects  in  the  saloons 
of  the  celebrated  Clichy  Club  ;  when  the  recriminations, 
the  reciprocal  accusations,  that  had  reached  the  utmost 
violence,  were  already  succeeded  by  deeds  of  violence 
against  patriots,  and  the  gainers  of  national  property, — 
our  troops  were  yet  everj'where  triumphant.  The  army 
of  the  Rhine  and  Moselle  under  the  orders  of  Moreau, 
the  army  of  the  Sambre  and  Meuse,  commanded  by 
Jourdan,  had  gloriously  crossed  the  Rhine  ;  they  were 
marching  into  the  heart  of  Germany  ;  the  army  of  Italy 
was  only  twenty  leagues  from  Vienna ;  at  Leoben,  Bona- 
parte signed  the  preliminaries  of  the  much  wished-for 
treaty  of  peace.  Without  compi'omising  the  negotiations, 
he  could  show  himself  touchy  about  mere  questions  of 
etiquette  ;  he  could  bluntly  refuse  to  let  the  name  of 
the  Emperor  of  Germany  precede  that  of  the  French 
Republic  in  the  protocols  ;  he  could  also,  when  General 
Meerwald,  and  the  Marquis  del  Gallo  talked  to  him 
about  gratitude,  answer,  without  a  boast,  in  the  following 


EPOCH    OF    THE    REVOLUTION.  67 

memorable  words  :  "  The  French  Republic  does  not  re- 
quire to  be  recognized  ;  it  is  in  Europe  what  the  sun  is 
on  the  horizon  :  so  much  the  worse  for  those  who  will 
not  see  and  profit  by  it."  Is  it  then  surprising,  Gentle- 
men, I  ask  you,  that  in  so  favourable  a  position  of  our 
foreign  affairs,  Carnot  believed  in  the  possibility  of  a 
conciliation  between  the  political  parties  into  which  the 
country  was  divided  ;  that  he  refused  (I  purposely  use 
his  own  words)  to  exorcise  danger  by  going  beyond  the 
limits  of  the  Constitution  ;  that  he  firmly  repelled  any 
thought  of  a  covp-cTetat, — a  very  convenient  way  as- 
suredly of  getting  out  of  a  scrape  ;  but  a  dangerous 
way,  and  one  that  almost  always  ends  by  becoming 
injurious  to  the  very  persons  who  expected  to  benefit 
by  it? 

I  should  have  much  wished.  Gentlemen,  to  have  en- 
tered more  deeply  into  an  examination  of  the  part  that 
Carnot  acted  at  that  critical  epoch  of  the  Revolution.  I 
have  not  neglected  any  thing  to  raise  at  least  a  corner  of 
the  veil  which  still  covers  an  event  that  so  greatly  in- 
fluenced the  fate  of  our  colleague,  and  that  of  the  country; 
but  my  efforts,  I  acknowledge,  have  been  unsuccessful. 
Documents  are  not  wanting,  but  they  almost  all  emanate 
from  writers  too  much  intei'ested,  either  in  excusing  or 
in  branding  the  18th  of  Fructidor,  not  to  be  suspected. 
The  recriminations  full  of  bitterness,  of  violence  against 
each  other,  to  which  some  old  colleagues  then  abandoned 
themselves,  have  reminded  me  of  that  wise  declaration 
by  Montesquieu  :  "  Do  not  listen  either  to  Father  Tour- 
nemine  or  to  me,  when  we  are  speaking  of  each  other, 
for  we  have  ceased  to  be  friends."  The  antecedents,  the 
opinions,  the  character,  the  known  and  avowed  actions  of 
the  various  persons  who  caused  the  coiip-d'etat, — or  be- 


68  CARNOT. 

came  the  victims  of  it,  would  not  have  been  any  better 
guide.  I  should  have  seen  Hoche  march  at  one  moment 
against  his  constant  and  zealous  protector,  against  him 
"who  had  saved  his  life  under  the  rule  of  Robespierre,  and 
who,  in  1793,  transformed  the  trimmings  of  the  young 
sergeant  into  the  epaulettes  of  a  full  general.  I  should 
have  found  Bonaparte  contributing  by  his  delegate  Auge- 
reau,  to  the  upsetting,  and  to  the  proscription  of  the  only 
Director  with  whom  he  had  continued  intimately  con- 
nected during  the  campaign  of  Italy.  I  should  have 
seen  him  on  his  journey  to  Geneva  have  the  banker 
Bontemps  arrested,  under  pretext  that  he  had  favour- 
ed the  escape  of  that  same  Carnot  to  whom  a  few 
months  before,  he,  Bonaparte,  wrote  from  Plaisance 
(20th  of  Floreal,  year  IV.),  from  Milan  (the  20th  of 
Prairial,  the  same  year),  from  Verona  (the  9th  of  Plu- 
viose,  year  V.)  :  "  I  owe  you  special  thanks  for  the  at- 
tention that  you  kindly  show  to  my  wife  ;  I  recommend 
her  to  you  ;  she  is  a  sincere  patriot,  and  I  love  her  to 
madness  ....  I  will  deserve  your  esteem  ;  I  beg  of 

you    to   continue  your   friendship  for  me The 

sweetest  recompense  for  the  fatigues,  the  dangers,  the 
chances  of  this  profession,  is  the  approbation  of  the  small 

number  of  men  whom  we  ajipreciate I  have 

alw^ays  had  to  rejoice  in  the  marks  of  friendship  that  you 
have  shown  to  me  and  mine,  and  I  shall  always  be  truly 

grateful  to  you  for  them The  esteem  of  a  small 

number  of  persons  like  yourself,  that  of  my  brother 
officers,  of  the  soldier,  interest  me  deeply." 

Of  the  two  sincere  Republicans  included  in  the  execu- 
tive Directory,  I  should  have  met  one  among  the  Fruc- 
tidorisants,  the  other  among  the  Fructidorises ;  the 
satrap  Barras — of  whom  it  might  have  been  said,  with- 


COUNCIL    OF    THE    FIVE-HDNDRED.  69 

out  exciting  contradiction,  that  he  was  always  sold,  and 
always  for  sale — would  have  oftered  himself  to  me  as 
the  friend,  as  the  ally,  or  at  least  as  the  intimate  confi- 
dant, of  the  austere,  the  honest  La  Revelliere  ;  I  should 
have  seen  that  same  Barras,  who  already,  perhaps,  at 
that  epoch,  corresponded  directly  with  the  Count  de 
Provence,  surrounded  by  a  crowd  of  myrmidons,  of 
whom  none,  be  it  said  in  passing,  afterwards  refused  the 
imperial  livery, — upset,  by  incessant  accusations  of  roy- 
alty, the  only  man  of  our  assemblies  who,  always  constant 
in  his  convictions,  battled  foot  by  foot  against  the  insati- 
able ambition  of  Bonaparte. 

Seeking  in  the  sequel  by  facts,  and  only  by  facts, 
whether  the  majority  of  the  counsellors  was  really 
factious ;  whether  the  counter-revolution  could  not  be 
avoided  but  by  a  coup-d' itat ;  in  a  word,  whether  the 
18th  of  Fructidor  was  inevitable,  I  should  have  found, 
and  this  notwithstanding  the  mutual  concessions  which 
the  authors  of  the  proscription  no  doubt  made,  as  in  the 
time  of  Octavius,  of  Lepidus,  of  Anthony, — I  should 
have  found  an  elimination,  or,  if  you  will,  a  filtering  of 
forty-one  members  only,  in  the  Council  of  the  Five-Hun- 
dred, and  of  eleven  in  the  Council  of  the  Elders. 

The  thread  that  could  safely  guide  the  historian  in 
this  labyrinth  of  contradictory  facts,  I  repeat  it,  I  have 
not  found.  The  memoirs  snatched  from  the  family  of 
Barras  by  order  of  Louis  XVIIL ;  the  memoirs  that 
were  left  by  La  Revelliere,  and  of  which  it  is  so  desir- 
able that  the  public  should  be  no  longer  deprived  ;  the 
confessions  which  on  the  other  hand,  we  have  a  right  to 
expect  on  the  part  of  some  of  the  victims  of  the  Direc- 
torial covp-(Vkat,  may,  perhaps,  dissii)ate  all  the  clouds. 
Would  to  God,  for  the  honour  of  the  country,  that  in  the 


70  CARNOT. 

end,  the  violent  and  illegal  mutilation  of  the  national  rep- 
resentation may  not  appear  to  be  the  exclusive  result  of 
the  animosities  and  personal  antipathies  excited,  or,  at 
least,  in  great  measure  fostered,  by  the  intrigues  of  several 
notorious  women.  Still  the  investigations  of  future  his- 
torians, however  extended  and  complicated  they  may  be, 
can  never  militate  against  the  perfect  uprightness  of  our 
co-academician.  Already  there  remain  no  vestiges  of 
the  accusations  detailed  in  the  official  report  presented  in 
the  year  VI.  to  the  Council  of  the  Five-Hundred  :  in  a 
few  pages,  Carnot  reduced  them  to  nought.  All  that 
malevolence  or  mere  preconception  dares  to  borrow  now 
from  the  pamphlet  elaborated  with  so  much  artifice  by 
Bailleul,  is  reduced  to  an  empty  reproach  coarsely  ex- 
pressed, and  which  I  should  have  disdained  to  mention, 
had  not  Carnot  himself  indicated  on  what  conditions  he 
accepted  it. 

Political  hacks  call  by  the  name  of  simpletons,  all  men 
who  would  disdain  such  advantages  as  are  bought  at  the 
expense  of  good  faith,  honesty,  and  morality.  But  we 
must  not  be  deceived ;  simpleton  is  the  polite  epithet ; 
blockhead  is  prefeiTcd  when  we  do  not  feel  ourselves 
bound  to  keep  within  limits  or  to  adhere  to  the  language 
of  good  society.  This  epithet,  disdainfully  cast  by  Bail- 
leul in  the  official  report,  had  cruelly  mortified  Carnot ; 
it  is  ironically  repeated  in  almost  every  page  of  our  col- 
league's answer.  He  says  in  one  part :  "  Yes  !  the 
blockhead  Aristides  is  chased  from  his  country  ;  the 
blockhead  Socrates  drank  hemlock ;  the  blockhead  Cato 
is  reduced  to  commit  suicide  ;  the  blockhead  Cicero  is 
assassinated  by  order  of  the  triumvirs.  Yes  !  the  block- 
head Phocion  is  also  led  to  the  scaffold,  but  glorying  ia 
having  to  undergo  the  fiite  reserved  in  all  ages  for  those 
who  serve  their  country  well." 


ESCAPE    FROM    THE    LUXEMBOURG.  71 

Carnot  escaped  from  the  Luxembourg  at  the  moment 
that  the  myrmidons  were  entering  his  room,  to  arrest 
him.  A  family  of  Burgundian  artisans  received  and 
concealed  him.  Those  whose  life  is  an  uninteiTupted 
series  of  privations,  know  well  how  to  compassionate 
misfortune.  Our  colleague  afterwards  sought  refuge  in 
the  house  of  M.  Oudot,  a  great  partisan  of  the  coup-rT etat 
on  the  18th  Fructidor ;  and  where,  from  that  date,  no 
one  would  have  thought  of  seeking  the  proscribed  Direc- 
tor. Carnot  had  not  yet  left  Paris,  when  his  name  was 
erased  from  the  list  of  the  members  of  that  national 
Institute,  to  the  creation  of  which  he  had  so  much  con- 
tributed. 

Some  laws  proclaimed  on  the  19th  and  20th  of  Fruc- 
tidoi",  year  V.,  declared  all  the  places  vacant  that  had 
been  held  by  the  citizens  struck  by  the  coup-d' etat  of  the 
18lh.  The  Minister  of  the  Interioi",  Letourneux,  there- 
fore wrote  to  the  Institute  enjoining  it  to  proceed  to  the 
naming  of  a  successor  to  Carnot.  The  three  classes 
then  proceeded  to  the  nomination  of  the  members  of 
each  class.  One  hundred  and  four  voters  took  part  in 
the  election ;  but  the  urn  did  not  receive  one  white  ball ! 

I  know,  Gentlemen,  how  much,  in  Revolutionary 
times,  the  most  upright,  the  most  firm  minds,  are  influ- 
enced by  public  opinion  ;  I  know  that  after  the  lapse  of 
time  that  separates  us  from  the  18th  of  Fructidor,  no 
one  can  conceive  that  he  has  a  right  to  blame  the  Insti- 
tute at  all  for  having  yielded  to  the  ministerial  orders  ; 
still,  I  will  here  express  freely  my  regret,  that  imperious 
circumstances  did  not  permit  our  honourable  predeces- 
sors, since  the  Fructidorian  era,  to  draw  a  marked  line 
of  distinction  between  the  politician  and  the  philosojdier. 
Under  the   Regency,  in  the  affair  of  the   Abbe   Saint- 


72  CARNOT. 

Pierre,  Fontenelle  had  already,  by  a  courageous  stroke, 
protested  against  the  powers  attempting  to  confound  that 
which  the  interests  of  science,  of  literature,  and  of  art 
bid  us  keep  for  ever  apart.  If,  in  the  year  V.  of  the 
Republic,  fifty-three  voters  had  had  the  manliness  to 
imitate  Fontenelle,  the  Institute  would  not  have  suffered 
such  cruel  mutilations  at  the  Restoration  ;  deprived  of 
the  support  afforded  by  unfortunate  precedents,  certainly 
not  many  ministers  would  have  entertained  the  unpar- 
donable thought  of  creating  an  Academy  of  Sciences  at 
Paris  without  Monge,  an  Academy  of  Fine  Arts  with- 
out David ! 

You  are  surprised,  no  doubt,  that  I  have  not  yet 
informed  you  of  the  name  of  the  person  wlio  succeeded 
Carnot  in  the  first  class  of  the  Institute  ;  well,  Gentle- 
men, it  is  because  I  have  refrained,  as  much  as  possible, 
from  performing  a  painful  duty.  When  it  proceeded  to 
elect  a  successor  to  one  of  its  founders,  to  one  of  its 
most  illustrious  members,  the  Institute  obeyed,  at  least, 
an  established  law  proceeding  from  the  powers  of  the 
State  ;  but  is  there,  I  ask  you,  any  consideration  in  the 
world  that  should  induce  a  man  to  accept  the  academic 
spoils  of  a  learned  victim  of  party  rage,  and  especially 
so,  when  that  man  is  General  Bonaparte  ?  Like  all  of 
you,  Gentlemen,  I  have  often  indulged  in  a  just  feeling 
of  pride,  on  seeing  the  admirable  proclamations  of  the 
army  of  the  East,  signed:  Member  of  the  Institute, 
General-in-Chief ;  but  a  heart-grief  followed  the  first 
sensation,  when  it  occurred  to  my  mind,  that  the  Member 
of  the  Institute  had  arrayed  himself  with  a  title  which 
had  been  torn  from  his  first  patron  and  friend. 

I  have  never  thought,  Gentlemen,  that  it  was  useful 
to  create  beings  of  ideal  perfection,  at  the   expense  of 


ESCAPE    FROM    GENEVA.  73 

truth  ;  and  this  is  the  reason  why,  notwithstanding  some 
friendly  advice,  I  have  persisted  in  divulging  what  you 
have  just  heard,  relative  to  the  nomination  of  (reneral 
Bonaparte  to  the  Institute.  "  But,"  said  a  Napoleonist 
to  me,  "  coming  from  you,  the  story  has  no  weight ;  for 
does  not  all  the  world  know  that  you  astronomers  seek 
to  find  spots  in  the  sun  ! "  Thus,  Gentlemen,  my  posi- 
tion has  given  me  the  j^rivilege  of  telling  truth  without 
offending  any  one,  which,  by  the  by,  is  extremely  rare  ! 

I  regret  not  being  able  to  discover  the  name  of  the 
generous  citizen  who  snatched  Carnot  from  his  retreat, 
and  carried  him  safely  in  his  postchaise  to  Geneva. 

On  arriving  in  that  city,  Cai'not  engaged  lodgings  at  a 
laundryman's,  under  the  name  of  Jacob.  Prudence  re- 
quired his  being  entirely  unknown  ;  but  the  wish  of 
getting  certain  news  from  his  beloved  country  carried 
the  day  ;  he  went  out,  he  was  recognized  in  the  street 
by  some  spies  of  the  Directory,  who  followed  him,  dis- 
covered his  retreat,  and  immediately  set  a  watch  on  it. 
Some  French  agents  who  had  influence  in  the  Genevese 
Republic,  exclaimed  loudly  that  he  ought  to  be  given  up 
to  the  laws  of  his  country,  and  even  made  an  official 
representation  to  the  Genevese  Government.  The  mao-- 
istrate  into  whose  hands  this  diplomatic  affair  fell,  was 
fortunately  a  man  of  feeling,  and  conscientious  withal, 
and  who  felt  what  a  great  blemish  would  be  inflicted  on 
his  country  thereby.  This  magistrate  was  named  M. 
Didier.  On  such  an  occasion,  Gentlemen,  it  would  be  a 
crime  not  to  cite  a  name  known  also  in  literature,  thus 
connected  with  a  humane  action.  M.  Didier  wrote  to 
Carnot ;  he  warned  him  of  his  danger,  entreated  him  to 
quit  the  house  immediately,  and  directed  him  to  a  spot 
on  the  lake  where  a  boatman  would  await  him,  to  take 


74  CARNOT. 

him  over  to  Nyon.  It  was  already  very  late ;  the  con- 
stables of  the  Directory  were  watching  their  prey.  Our 
colleague  goes  direct  to  his  host,  and,  without  any  pre- 
amble, asks  pardon  for  having  introduced  himself  into 
his  house  under  a  false  name.  "  I  am  proscribed,  I  am 
Carnot,  they  are  going  to  arrest  me  ;  my  fate  is  in  your 
hands  :  will  you  save  me  ?  "  said  he.  The  honest  laun- 
dryman  replied,  "  Without  any  doubt."  Immediately 
he  muffled  up  Carnot  with  a  blouse,  Avith  a  cotton  cap, 
with  a  dossier ;  he  lays  on  his  head  a  large  loose 
bundle  of  dirty  linen,  which  hung  down  to  the  shoulders 
of  the  pretended  Jacob,  and  hid  his  figure.  By  favour 
of  such  a  disguise,  the  man  who  a  short  time  before  by 
writing  a  few  lines  could  scatter  or  arrest  in  their  march 
armies  commanded  by  a  Marceau,  a  Hoche,  a  Moreau,  a 
Bonaparte  ;  to  shed  hope  or  fear  at  Naples,  at  Rome,  at 
Vienna  ;  now — melancholy  vicissitude  of  things  hei'e 
below, — having  borrowed  the  trappings  of  a  laundry- 
man's  labourer,  reaches  in  safety  the  little  boat,  in  which 
he  is  to  escape  from  being  sent  a  prisoner  back  to  France. 
In  the  boat,  a  new  and  strange  emotion  awaited  Carnot. 
In  the  boatman  appointed  by  M.  Didier  he  recognizes 
that  same  Pichegru,  whose  culpable  intrigues  had  per- 
haps rendered  the  ISth  Fructidor  inevitable.  During 
all  the  time  occupied  in  crossing  the  lake,  not  a  single 
word  was  exchanged  between  the  two  proscribed  men. 
Indeed,  the  time,  the  place,  the  circumstances  were  not 
suitable  for  political  debates,  for  recriminations  !  Car- 
not, moreover,  had  soon  to  congratulate  himself  on  his 
reserve ;  on  reading  the  French  journals  at  Nyon,  he 
learnt  that  he  had  been  deceived  by  a  fortuitous  resem- 
blance ;  that  his  travelling  companion,  far  from  being  a 
general,  had  never  manoeuvred  any  thing  more  than  his 


RETURN    TO    FRANCE.  75 

frail  boat,  and  that  Pichegru,  being  arrested  by  Auge- 
reau,  was  expecting  to  be  taken  back  to  one  of  the  pris- 
ons in  Paris.  Carnot  was  still  at  Nyon  when  Bonaparte, 
returning  from  Italy,  passed  through  that  little  town  on 
his  way  to  Rastadt.  Like  all  the  other  inhabitants,  he 
illuminated  his  windows  to  do  homage  to  the  general. 

If  the  plan  that  I  have  proposed  to  myself  were  to 
allow  me  at  present  to  speak  of  Carnot's  rare  and  sin- 
cere modesty,  I  hope  his  little  illumination  at  Nyon 
would  not  be  opposed  to  me.  When  he  placed  two 
candles  in  his  window,  in  honour  of  victories  to  which 
he  had  contributed  by  his  orders,  or  at  least,  by  his 
counsels,  Carnot  proscribed,  Carnot  labouring  under  the 
menace  of  a  forced  journey  back  to  Paris,  and  then  of 
exile  in  the  deserts  of  Guyana,  must  certainly  have 
been  agitated  by  far  different  sentiments  ;  nor  can  we 
presume  that  pride  showed  itself  in  any  of  them. 

18th  BRUMAIRE. — RETURN  OF    CARNOT    TO    FRANCE. 

HIS     NOMINATION     TO     BE     MINISTER    OF    WAR. HIS 

DISMISSAL. HIS    APPOINTMENT    TO    THE  TRIBUNATE. 

During  upwards  of  two  years,  Carnot  had  disappeared 
from  the  arena  of  politics  ;  during  upwards  of  two  years 
he  had  lived  at  Augsbourg  under  a  feigned  name,  ex- 
clusively occupied  in  the  cultivation  of  the  sciences  and 
of  literature,  when  General  Bonaparte  returned  from 
Egypt,  and  with  a  breath  reversed  the  18th  Brumaire, 
a  government  that  had  never  been  able  to  take  root  in 
the  country.  One  of  his  first  acts  was  his  recalling  the 
iHustrious  exile,  and  nominating  him  to  be  Minister  of 
War.  The  enemy  was  then  at  our  gates.  Carnot  did 
not  hesitate  to  accept ;  but  a  few  months  after,  when  the 
immortal  victories  of  Marengo  and  of  Hohenlinden  had 


76  CAKNOT. 

given  an  incontestable  superiority  to  our  arms,  when  the 
independence  of  the  country  was  again  assured,  Carnot 
resif^ned  his  ajipointment.  He  would  not  consent  to 
appear  an  accomplice  in  the  changes  that  were  prepar- 
ing in  the  form  of  the  government.  Accordingly,  on 
the  16th  Vendemiaire,  year  IX.,  he  wrote  as  follows: 
"Citizen  Consuls,  I  again  send  you  my  resignation ;  I 
beg  you  will  not  defer  accepting  it." 

It  is  not  from  a  trifling  cause  that  people  part  thus 
laconically.  The  letter  I  have  just  given  was  a  corollary 
of  the  earnest  disputes  that  were  daily  occurring  between 
the  Republic  and  the  Empire,  in  the  persons  of  tJie  First 
Consul  and  the  Minister  of  War. 

Recalled  to  public  aflfiiirs  as  a  Tribune  in  1802,  Car- 
not opposed  the  creation  of  the  Legion  of  Honour.  He 
thinks — I  was  going  to  say,  he  foresees — that  a  distinc- 
tion bestowed  without  inquiry  by  the  uncontrolled  will  of 
one  man,  will  end,  notwithstanding  its  imposing  title,  and 
according  to  the  natural  course  of  things  in  this  world, 
by  no  longer  being  any  more  than  the  means  of  attaching 
followers,  and  reducing  to  silence  a  swarm  of  little  vani- 
ties. Carnot  also  with  all  his  might  opposed  the  creation 
of  a  Consulate  for  life  ;  but  it  was  especially  at  the 
moment  when  it  was  proposed  to  raise  Bonaparte  to  the 
Imperial  Tiirone,  that  he  redoubled  his  energy  and 
ardour.  History  has  already  recorded  his  noble  words  ; 
she  will  also  say,  that  surrounded  by  old  Jacobins,  sur- 
rounded even  by  those  same  men  who,  on  the  18th 
Fructidor,  had  persecuted  him  as  a  royalist,  Carnot  re- 
mained standing  nearly  alone  in  the  midst  of  the  general 
apostasy,  as  if  at  least  to  prove  to  the  world  that  politi- 
cal conscience  is  not  quite  an  empty  word. 

The  Tribunate  was  soon  suppressed.     Carnot  retii'ed 


GEOMETRY    OF    POSITION.  77 

again  into  private  life  ;  I  will  not  say  with  joy,  Gentle- 
men, for  in  our  colleague's  bosom  the  virtues  of  a  citizen 
always  occupied  the  principal  place  ;  for  he  had  hoped, 
that,  like  another  Washington,  General  Bonaparte  would 
avail  himself  of  this  unique  opportunity  to  found  in 
France  order  and  liberty  on  a  stable  basis  ;  for  no  man 
initiated  in  public  aifairs,  and  endowed  with  some  fore- 
sight, could  without  uneasiness  see  the  reins  of  govern- 
ment placed  beyond  control,  and  without  guarantee,  in 
the  hands  of  an  ambitious  soldier.  I  shall  be  able  at 
least  to  show  you  that  Carnot's  leisure  was  nobly  and 
gloriously  employed. 

PUBLICATION    OF    THE    GEOMETRY    OF    POSITION. 

There  is  a  story  told  of  a  young  student  who,  almost 
discouraged  with  some  difficulties  inherent  in  the  first 
elements  of  mathematics,  went  to  consult  D'Alembert, 
when  this  great  geometer  answered  him,  "  Go  on,  sir, 
go  on,  and  faith  will  come  to  you."  * 

The  advice  was  good,  and  geometers  have  followed  it 
generally :  they  "  go  on,"  also  ;  they  perfect  methods, 
and  multiply  the  applications  of  them,  without  pre- 
occupying themselves  about  the  two  or  thi-ee  points 
whei-e  the  metaphysics  of  the  science  offer  obscurities. 
Shall  it  be  said  on  that  account  that  the  filling  up  of 

*  D'Alembert's  advice  requires  much  explanation;  as  it  stands  it 
would  be  a  good  motto  for  Jesuits.  It  reads  altogether  contrary  to 
the  spirit  of  mathematics,  where  one  step  is  made  sure  of  before 
looking  out  for  another, — where  the  self-secured  truth  is  in  place  of 
smy  faith.  It  is  meant,  perhaps,  to  encourage  the  student  to  disregard 
contingent  apparent  puzzles;  it  should  then  be  rendered,  "Hold  on 
in  the  path  whose  truth  is  evident  to  you,  and  after  a  time  you  will 
get  a  clearer  view  of  those  collateral  circumstances  which  now  con- 
fuse you,  while  looking  every  way  at  once." — Translator. 


78  CARNOT. 

these  gaps  should  be  altogether  neglected  ?  Such  was 
not  Carnot's  view.  "We  have  already  seen  him  devoting 
the  short  moments  of  repose  Avhich  his  Directorial  duties 
left  him  to  the  metaphysics  of  the  Infinitesimal  Calculus  ; 
the  suppression  of  the  Tribunate  will  permit  him  to  sub- 
mit to  similar  investigations  an  equally  arduous  question 
— that  of  negative  quantities. 

It  often  happens  that,  after  having  reduced  a  problem 
to  the  form  of  an  equation,  analysis  offers  you  some  neg- 
ative numbers  amongst  the  solutions  sought  for  ;  for 
example  minus  10,  minus  50,  minus  100  ;  these  solutions 
the  ancient  analysts  did  not  know  how  to  interpret. 
Vieta  himself  neglected  them  as  absolutely  useless  and 
insignificant.  By  degrees  they  got  into  the  habit  of  re- 
garding negative  numbers  as  quantities  less  than  zero. 
Newton  and  Euler  gave  no  other  definition  of  them 
(  Universal  Arithmetic,  and  Introduction  to  Infinitesimal 
Analysis).  This  notion  has  in  modern  times  introduced 
itself  into  the  vulgar  tongue :  the  merchant  on  the  most 
petty  scale  understands  exactly  the  position  of  a  corre- 
spondent who  announces  to  him  negative  profits ;  poetry 
has  also  given  its  sanction  to  the  same  thought,  as  we 
see  in  these  two  verses,  by  which  Chenier  stigmatized 
his  political  enemies,  the  editors  of  the  3Iercure  de 
France  : — 

"  Which  these  lettered  dwarfs  have  done,  who  without  literature, 
Beneath  noHenUty.  sustain  the  MtrcureJ'''  * 

"Well,  Gentlemen,  it  is  a  notion  thus  supported  by  the 
authority  of  the  greatest  geometers  of  modern  times, 
consecrated  by  the  assent  of  one  who  has,  they  say,  more 

*  "  Qu'ont  fait  ces  iiains  ]ettr(5s  qui,  sans  litterature, 
Au-dessQus  du  neant,  soutiennent  le  Mercure.'''' 


GEOMETRY    OF    POSITION.  79 

talent  than  Voltaire,  or  Rousseau,  or  Bonaparte,  and  by 
the  assent  of  the  generality  of  the  public,  that  Carnot 
has  combated  with  the  keen  weapons  of  logic. 

Certainly  nothing  is  more  simple  than  the  notion  of  a 
negative  quantity,  when  it  is  attached  to  a  positive  quan- 
tity greater  than  itself;  but  a  detached  negative  quantity, 
a  detached  quantity  looked  upon  as  isolated,  must  it  be 
really  considered  less  than  zero,  and  a  fortiori,  inferior 
to  a  positive  quantity  ?  Carnot,  agreeing  on  this  point 
with  D'Alembert,  who,  most  amongst  the  great  mathe- 
maticians of  the  last  century,  occupied  himself  with  the 
philosophy  of  science,  maintains  that  negative  isolated 
quantities  figure  in  operations  admitted  by  everybody, 
and  in  which,  nevertheless,  it  would  be  impossible  to 
suppose  them  beneath  zero.  Notwithstanding  the  dry- 
ness of  such  details,  I  will  quote  one  of  these  operations. 
No  one  denies  that 

-j_  10  is  to  —  10  as  —  10  is  to  -f  10. 

In  order  that  four  numbers  should  form  a  proportion, 
it  is  necessary,  and,  in  ftict,  it  suffices  that,  if  the  four 
numbers  are  fittingly  ranged  in  order,  the  product  of  the 
extremes  should  be  equal  to  that  of  the  means.  "We 
must  not  be  startled  at  this.  Gentlemen ;  the  principle  I 
call  in  here,  is  no  other  than  that  of  the  famous  rule  of 
three  of  the  teachers  of  writing  and  arithmetic  ;  it  is  the 
principle  of  the  calculation  which  is  executed  some  hun- 
dreds of  thousands  of  times  daily  in  the  shops  of  the 
metropolis.  Now,  in  the  proportion  which  I  have  just 
cited,  the  product  of  the  extremes  is  -|-  100,  as  it  is  also 
of  the  means  ;  therefore 

4-  10  :  —  10  ::  —  10  :  -f-  10. 

Nevertheless,  if  -\-  10,  the  first  term  of  the  proportion, 
surpasses  the  second  term  —  10,  it  is  impossible  to  sup- 


80  CARNOT. 

pose  at  the  same  time  that  —  10,  the  first  term  of  the 
second  ratio,  surpasses  -)-  10,  the  second  term  of  the 
same  ratio ;  —  10  cannot  be,  at  the  same  time,  both  infe- 
rior and  sujierior  to  -j-  10.* 

Such  is,  in  substance,  one  of  the  principal  arguments 
on  which  our  member  grounds  his  view,  that  the  notion 
of  absolute  or  comparative  magnitude  should  not  be  ap- 
plied to  negative  quantities  any  more  than  to  imaginary 
ones  ;  that  we  cannot  examine  whether  they  are  greater 
or  less  than  zero  ;  that  they  must  be  considered  "as 
creations  of  our  reason,  as  mere  algebraical  forms." 

"When  the  genius  of  Descartes  had  shown  that  the  posi- 
tions of  all  possible  curves,  their  forms,  and  the  whole  of 
their  properties,  might  be  exactly  included  in  analytical 
equations,  the  question  of  negative  quantities  presented 
itself  under  an  entirely  new  light.    The  illustrious  philos- 

*  —  10  is  neither  inferior  nor  superior  to  -)-  10;  it  is  equal  to  it; 
though  not  algebraically  =;  but  in  taking,  as  our  author  does,  the 
sense  of  mathematical  formulas,  —  10  is  just  as  good  and  as  strong  in 
its  way  as  +  10  in  its  other  way.  Indeed  —  and  +  are  merely  sym- 
bols of  action  one  way  or  the  other;  notwithstanding  the  ordinary 
translation  of  minus,  —  being  "  less,"  whereas  it  simply  means  nega- 
tive, the  opposite  of  positive.  And  though  it  is  most  habitual  to  our 
ideas  to  consider  every  thing  in  a  positive  light,  the  negative  value  is 
just  as  real;  a  correct  appreciation  of  it  only  requiring  the  knowledge 
of  where  the  zero  of  the  peculiar  subjects  treated  of  is  placed,  which 
should  always  be  one  of  the  data  in  a  mathematical  question;  thus 
10  feet  below  the  level  of  the  sea  are  just  as  efficient  as  10  feet  above, 
and  10  degrees  below  any  level  in  the  thermometer  are  a  perfect  match 
for  10  degrees  above.  In  fact,  —  10  may  be  less  than  +  10  in  our 
usual  manner  of  viewing  positive  things;  yet  mathematically  and 
truly  it  is  not  less,  nor  greater,  hut  just  as  great.  Perhaps  calling 
a  —  quantity  less  than  nothing,  has  occasioned  a  confusion  of  terms ; 
for  it  is  merely  a  quantity  on  the  other  side  of  zero,  which  is  only  a 
symbol  of  equilibrium,  or  of  no  power  one  way  or  the  other.  The 
place  and  value  of  zero  depend  on  the  class  of  subjects  treated  of,  and 
are  previously  known  from  experience. —  Translator. 


GEOMETRY    OP    POSITION.  81 

opher  himself  established  in  principle,  that  in  geometry 
these  quantities  only  differ  from  the  positive  in  the  direc- 
tion of  the  lines  on  which  they  ought  to  be  reckoned. 
This  profound  and  simple  view  is  unfortunately  subject 
to  some  exceptions.  Let  us  suppose,  for  example,  that 
it  is  proposed  to  draw  from  a  point  without  a  circle,  a 
straight  line  so  situated  that  the  portion  comprised  within 
the  circle  shall  have  a  given  length.  If  the  distance  be- 
tween the  point  from  wliich  the  line  is  to  be  drawn,  and 
the  point  in  the  circumference  which  it  will  first  meet,  be 
taken  as  unknown,  the  calculation  gives  two  values  :  the 
one,  positive,  corresponds  with  the  first  point  of  the  inter- 
section of  the  straight  line  sought  with  the  circle ;  the 
other,  negative,  determines  the  place  of  the  second  inter- 
section. Now  who  does  not  see  *  that  these  two  lengths, 
the  one  positive,  the  other  negative,  must  be  measured 
from  the  same  side  of  the  point  from  which  the  straight 
line  was  drawn  ? 

Carnot  proposed  to  himself  to  cause  these  exceptions 
to  disappear.  He  does  not  admit  isolated  negative  solu- 
tions in  geometry  any  more  than  in  algebra.  To  him 
these  solutions,  taking  away  their  signs,  are  the  differ- 
ences of  two  other  absolute  quantities  ;  the  one  of  those 
quantities  which  was  the  greatest  in  the  case  reasoned 
on,  only  becomes  the  smallest  when  the  negative  root 

*  "  Who  does  not  see  V  "  We  cannot  say  that  we  do,  nor  can  any- 
body else,  perhaps,  who  has  not  the  calculation  before  him.  There 
are  many  ways  of  measuring  distances  about  a  circle ;  and  two  differ- 
ent lines  in  it  amounting  to  the  same  effect  can  -be  so  often  drawn," 
that  those  wishing  to  be  convinced  would  prefer  hearing  more  about 
it;  at  any  rate  it  is  easier  to  suppose  there  is  some  thing  misunderstood 
in  the  working  of  the  problem,  or  in  the  meaning  of  its  solution,  than 
that  the  whole  system  of  notation,  on  which  all  former  results  depend, 
should  be  wrong. —  Trandalor. 
4  * 


82  CARXOT. 

appears.  In  geometry  then,  as  in  algebra,  the  negative 
root  taken  with  the  sign  -f-,  is  the  solution  of  a  different 
question  from  that  which  was  put,  or,  at  any  rate,  from 
that  which  it  was  exclusively  desired  to  put,  in  the  equa- 
tion. How  is  it  now  that  problems  foreign  to  the  par- 
ticular one  which  the  geometer  wished  to  resolve,  mix 
themselves  up  with  it :  that  analysis  answers  with  deplo- 
rable fertility  to  questions  which  have  not  been  put  to  it ; 
that  if  its  aid  is  sought,  for  example,  to  determine  the 
ellipse  whose  area  is  a  maximum  amongst  all  those  wdiich 
can  be  drawn  through  four  stated  points,  it  gives  three 
solutions,  whilst  evidently  there  is  only  one  good,  admis- 
sible, and  capable  of  application  ;  that  without  the  knowl- 
edge and  against  the  will  of  the  calculator,  it  thus  groups, 
in  this  particular  case,  a  problem  relating  to  the  limited 
area  of  the  ellipse  with  one  concerning  the  hyperbola,  a 
curve  with  indefinite  branches,  and  therefore  with  indefi- 
nite area?  Here  is  what  required  clearing  up,  here  is 
that  of  which  the  theory  of  the  co-relation  of  figures  and 
the  Geometry  of  Position,  which  Carnot  has  connected 
with  his  very  ingenious  views  on  negative  quantities,  give 
generally  easy  solutions. 

Since  these  labours  of  our  member,  every  one  thus 
applies  without  scruple,  the  formula  established  on  one 
particular  state  of  any  curve,  to  all  the  different  foi'ms 
which  that  curve  may  take.  Those  who  will  read  the 
works  of  the  ancient  mathematicians,  the  collection  of 
Pappus,  for  example  ;  those  who  will  observe,  even  in 
■  the  last  century,  two  celebrated  geometers,  Sirason  and 
Stewart,  giving  as  many  demonstrations  of  a  proposition 
as  the  figure  to  which  it  related  could  take  different  posi- 
tions or  forms  by  the  disarrangement  of  its  parts  ;  they 
will,  I  say,  estimate  Caruot's  service  to  geometry  as  very 


GEOMETRY    OF    POSITION.  83 

high.  I  wish  I  could  say,  with  the  same  truth,  that  the 
views  of  our  member  had  more  or  less  filtered  into  tliat 
multitude  of  elementary  treatises  which  appears  every 
year,  and  that  they  had  contributed  towards  perfecting 
instruction  ;  but  on  this  point  I  can  only  express  my  re- 
gret. In  the  present  day  the  philosophical  part  of  science 
is  very  much  neglected  ;  the  means  of  shining  in  an  ex- 
amination, or  an  assembly,  hold  the  first  place  ;  with 
some  rare  exceptions,  professors  think  much  more  of 
familiarizing  their  pupils  with  the  mechanism  of  the  cal- 
culus, than  of  causing  them  to  penetrate  to  its  principles. 
In  fact,  I  almost  think  we  might  say  of  certain  persons, 
that  they  employ  analysis  in  the  same  manner  as  most 
manufacturers  do  the  steam-engine,  without  reflecting  on  ' 
its  mode  of  action.  And  let  it  not  be  supposed  that  this 
faulty  style  of  instruction  is  a  necessary  sacrifice  to  the 
reigning  passion  of  our  age,  the  rage  for  going  fast  in 
every  thing,  Have  not  illustrious  members  of  this  Acad- 
emy shown,  in  justly  celebrated  works  on  geometry  and 
statics,  that  extreme  exactness  does  not  exclude  concise- 
ness ? 

Carnot's  Geometry  of  Position  would  not  have  the  high 
merit  which  I  have  attributed  to  it,  with  regard  to  the 
metaphysics  of  science,  if  it  were  not  also  the  origin  and 
base  of  the  progress  which  geometry,  cultivated  after  the 
manner  of  the  ancients,  has  made  in  tlie  last  thirty  years 
in  France  and  Germany.  The  numerous  properties  of 
space  which  our  member  has  discovered,  show  to  all  eyes 
the  power  and  fecundity  of  the  new  methods  with  which 
he  has  endowed  science.  Permit  me  to  justify  by  some 
quotations  the  favourable  opinion  which  I  have  formed  of 
the  methods  of  investigation  discovered  by  Carnot. 

"If  at  a  given  point  there  be  imagined  three  planes 


84  CARNOT. 

perpendicular  to  one  another  which  intersect  a  sphere, 
the  sum  of  the  areas  of  the  three  circles  forming  the  inter- 
sections will  always  be  the  same,  whatever  direction  be 
given  to  these  planes  :  provided  that  they  all  three  cut 
the  sphere." 

"In  every  trapezium,  the  sum  of  the  squares  of  the 
diagonals  is  equal  to  the  sum  of  the  squares  of  the  sides 
which  are  not  parallel,  plus  twice  the  pi'oduct  of  the  par- 
allel sides." 

"In  every  plane  or  uneven  quadrilateral  figure,  the 
sum  of  the  square  of  the  two  diagonals  is  double  the  sum 
of  the  squares  of  the  two  straight  lines  which  join  the 
centres  of  the  opposite  sides." 

I  shall  have  attained  my  end  if  these  quotations,  which 
I  could  multiply  to  any  amount,  inspire  professors  of 
mathematics  with  the  desire  of  seeing  for  themselves,  in 
Carnot's  Geometry  of  Position,  how  easily  all  these  curi- 
ous theorems  flow  from  the  methods  of  our  illustrious 
member. 

CARNOT    INVENTOR    OF   A   NEW    SYSTEM    OF    FORTIFICA- 
TION. 

There  would  be  a  gap  in  this  biography  which  would 
justly  attract  your  criticism,  if,  notwithstanding  the  many 
different  points  of  view  from  which  I  have  already  con- 
sidered the  imposing  figure  of  Carnot,  I  should  neglect  to 
speak  to  you  of  the  military  engineer,  of  the  inventor  of 
a  new  system  of  fortification. 

You  doubtless  recollect  the  violent  arguments  which 
Carnot  had  to  sustain,  from  the  time  of  his  entering  on 
the  military  career,  witli  the  chiefs  of  the  army  to  wliich 
he  belonged.  An  upright  and  inflexible  character  already 
made  him   repel    the    heavy   yoke   of  esprit   de   corps. 


NEW    SYSTEM    OF    FORTIFICATION.  85 

Mature  age  did  not  contradict  so  honourable  a  debut. 
Carnot  also  found,  in  his  exalted  mind,  the  secret  of  ex- 
tricating himself  from  the  sometimes  rather  burlesque 
preoccupations  of  men  exclusively  given  up  to  one  special 
pursuit.  Even  officers  of  engineers  have  not  always 
avoided  these  inconsistencies.  They  also  sometimes  ex- 
tend to  exaggeration  the  consequences  of  an  excellent 
principle.  Some  have  been  seen — I  am  certain  at  least 
of  having  heard  so — some  have  been  seen,  who  do  not 
cross  one  valley,  who  do  not  surmount  one  hill,  who  do 
not  rise  over  one  ridge  of  ground,  without  forming  the 
project  of  establishing  there  a  large  fortification,  or  a 
crenated  castle,  or  a  simple  redoubt.  The  idea  tiiat  with 
the  existing  facilities  of  communication  each  point  of  the 
territory  may  become  a  field  of  battle,  unceasingly  besets 
them  ;  it  is  on  this  account  that  they  oppose  the  opening 
out  of  roads,  the  construction  of  bridges,  the  cutting  down 
of  woods,  the  draining  of  marshes.  Fortified  towns  never 
appear  complete  to  them  ;  each  year  they  add  new  and 
expensive  erections  to  those  that  centuries  had  already 
accumulated.  The  enemy  would  doubtlessly  have  a  great 
deal  to  do  to  overcome  all  the  narrow  and  tortuous  de- 
files, all  the  crenated  gates,  all  the  drawbridges,  all  the 
palisades,  all  the  sluices  for  managing  the  water,  all  the 
ramparts,  all  the  demilunes  which  unite  modern  fortresses  ; 
but  in  awaiting  an  enemy  who  may  never  appear,  the 
inhabitants  of  some  fifty  large  cities  are  deprived,  from 
generation  to  generation,  of  certain  enjoyments,  of  certain 
conveniences  which  render  life  sweeter,  and  which  are 
freely  enjoyed  in  the  most  obscure  village. 

As  to  the  rest,  harsh  words  shall  never  proceed  from 
me,  blaming  the  prejudices,  if  they  are  prejudices,  in- 
spired   by   the    most    noble  of  sentiments,   tlie    love    of 


86  CARNOT. 

national  independence.  In  every  thing,  howevei*,  mod- 
eration is  requisite.  Does  not  economy  when  pushed 
to  the  extreme  become  hideous  avarice  ?  Does  not 
pride  degenerate  into  vanity  ;  politeness  into  affectation  ; 
freedom  into  rudeness  ?  It  is  by  weighing  in  exact 
scales  the  good  and  the  evil  resulting  from  all  human 
inventions,  that  we  keep  the  path  of  true  wisdom.  It  is 
thus  that,  despite  the  sovereignty  of  example  and  habit, 
despite  the  influence,  generally  so  powerful,  of  uniform, 
the  officer  of  engineers,  Carnot,  always  studied  important 
problems  of  fortification. 

In  1788,  some  French  officers,  enthusiastic  to  delirium 
respecting  Frederic  the  Great's  campaigns,  loudly  pro- 
claim the  entire  inutility  of  fortresses.  Govei'nment 
seems  to  accede  to  this  strange  opinion ;  it  does  not  yet 
oi"der  the  demolition  of  those  ancient  and  glorious  walls  ; 
but  it  allows  tliem  to  fall  of  themselves.  Carnot  with- 
stands the  general  bias,  and  sends  a  memoir  to  M.  de 
Biienne,  Minister  of  War,  in  which  the  question  is 
examined  in  all  its  phases  with  a  boldness  of  thought, 
an  ardour  of  patriotism  so  much  the  more  worthy  of 
remark,  because  such  examples  had  then  become  very 
rare.  It  shows  that  in  a  defensive  war,  the  only  sort 
that  he  advises,  the  only  one  that  he  thinks  legitimate, 
our  northern  fortresses  might  be  regarded  as  equal  to 
the  aid  of  a  hundred  thousand  men  of  the  regular  army; 
that  a  kingdom  surrounded  by  rival  nations  is  always  in 
a  precarious  state  when  it  has  troops  only  without  for- 
tresses. Then,  entering  on  the  financial  question,  Car- 
not affirms  (this  result  I  am  sure  will  astonish  my  audi- 
ence, as  it  astonished  me  also),  Carnot  repeatedly  affirms, 
that  far  from  being  a  gulf  into  wliich  the  treasures  of  the 
state  were  continually  being  lavished,  the  numerous  for- 


NEW    SrSTEM    OF    FORTIFICATION.  87 

tresses  of  the  kingdom  from  the  beginning  of  monarchy, 
from  the  foundation  of  the  oldest,  have  not  cost  as  much 
as  the  cavah-y  alone  of  the  French  army  during  twenty- 
six  years  ;  and  pray  remark  that  at  the  time  when  Carnot 
wrote  this  memoir,  exactly  twenty-six  years  had  elapsed 
without  our  cavalry  having  drawn  their  swords. 

Well,  Gentlemen,  having  become  a  member  of  the 
Legislative  Assembly,  this  ardent  advocate  for  fortresses 
proposed,  whatever  may  have  been  said  about  it,  not  the 
complete  destruction  of  the  special  and  independent  for- 
tifications, backed  by  cities  and  called  citadels,  but  the 
demolition  only  of  those  ramparts  that  before  isolated 
them.  Assuredly  the  certainty  of  there  being  a  place  of 
safe  retreat  must,  in  a  time  of  siege,  excite  the  soldier  to 
prolong  the  defence  and  run  the  hazardous  chance  of 
assaults ;  but  by  the  side  of  this  advantage,  citadels 
appeared  to  the  mind  like  real  Bastilles,  the  garrisons 
of  which  could  thunder  on  the  towns,  claim  ransom  from 
them,  or  make  them  submit  to  any  of  their  caprices. 
This  reflection  prevailed  in  the  mind  of  Carnot,  who  was 
an  eminently  good  citizen.  The  officer  of  engineers 
proscribed  citadels,  and,  despite  loud  clamours,  his  con- 
scientious opinion  prevailed. 

This  is  not  quite  the  case  with  the  new  systems  of 
fortifications,  and  of  defence,  proposed  by  our  colleague. 
They  have  only  thus  far  made  proselytes  among  for- 
eigners. Is  it  wrong,  or  is  it  reasonable,  that  our  clev- 
erest officers  should  reject  them  ?  God  forbid  that  I 
should  venture  to  cut  short  this  question.*     All  that  I 

*  Probably  the  author  is  alarmed  at  the  difliculty  and  responsibility 
of  deciding;  otherwise  he  ought,  as  a  biographer,  necessarily  to  give 
some  estimate  of  the  value  of  all  the  works  of  the  subject  of  his 
memoir. —  Translaior. 


88  CARNOT. 

can  undertake  is,  to  show  in  what  it  consists,  and  even 
to  be  understood  I  shall  have  to  make  a  fresh  appeal  to 
your  indulgent  attention. 

The  most  ancient  fortifications,  the  earliest  ramparts, 
were  simple  walls,  more  or  less  thick,  encircling  towns, 
and  thus  forming  continuous  inclosures  pierced  with  a 
small  number  of  gates,  for  the  entrance  and  exit  of  the 
inhabitants.  In  order  to  render  escalading  them  diffi- 
cult, these  ramparts  were  very  high  on  the  outer  side 
towards  the  country ;  besides  this,  a  ditch,  capable  of 
being  filled  with  water,  generally  divided  them  from  it. 

The  very  ramparts  themselves,  even  in  their  highest 
portion,  were  of  a  certain  breadth.  It  was  there  that 
the  population  of  the  towns  collected  in  cases  of  attack. 
It  was  from  thence  that,  partly  hidden  behind  a  low  wall 
now  called  a  parapet.,  they  threw  a  shower  of  missiles  on 
the  assailants.  The  most  timid  even  had  the  advantage 
of  not  descrying  the  enemy  but  through  narrow  aper- 
tures, that  are  still  seen  in  modern  fortifications  under 
the  name  of  loopholes  or  meurtrieres. 

The  besieger  did  not  begin  to  be  redoubtable  but 
from  the  moment  when,  having  reached  the  foot  of  the 
ramparts,  he  could,  by  means  of  tools,  engines,  or  ma- 
chines, sap  their  foundations.  To  act  then  freely  and 
vigorously  against  him  was,  for  the  besieged,  an  indis- 
pensable condition  of  a  good  defence.  Now,  let  us  imag- 
ine to  ourselves  a  soldier  placed  on  the  summit  of  the 
wall ;  he  will  evidently  not  be  able  to  perceive  the  foot 
of  it  without  leaning  forward,  without  leaving  nearly 
his  whole  body  exposed,  without  losing  the  advantages 
offered  him  by  the  parapet,  without  the  shelter  of  which 
he  could  not  have  thrown  his  arrows  but  by  exposing 
himself  to  the   well-aimed   shots  of   the    enemy  below. 


ADYANTAGE    OF    TOWERS.  89 

Let  US  add  that,  in  such  an  uneasy  position,  a  man  has 
neither  power  nor  address.  To  remedy  some  of  these 
inconveniences,  they  crowned  this  sort  of  wall  with  a 
construction  which  the  architects  called  corbels,  and  upon 
which  the  salient  parapets  rested.  Then  the  hollows, 
the  openings,  or  if  we  must  recur  to  the  technical  term, 
the  machicolations  comprehended  between  the  parapet 
and  the  rampart,  became  a  means  of  throwing  down 
stones  and  burning  substances,  &c.  on  those  who  were 
trying  to  sap  the  w^alls  or  escalade  them. 

To  strike  the  enemy  unremittingly,  when  he  reaches 
the  foot  of  the  rampart  of  a  town,  is  undoubtedly  excel- 
lent ;  but  to  prevent  his  advancing  so  far  would  be  still 
better.  They  approached  this  better  method,  without, 
however,  entirely  attaining  it,  by  constructing  at  various 
distances,  along  the  wall  of  the  city,  large  round  or 
polygonal  towers,  forming  very  salient  points.  If  we  in 
imagination  carry  ourselves  behind  the  parapet  of  the 
platforms  with  which  those  towers  were  crowned,  it  will 
be  easy  to  perceive  that  without  leaning  forward,  with- 
out much  exposure,  by  much  less  exposure  than  the 
assailants  undergo,  the  garrison  of  each  tower  could 
observe  the  next  tower  from  top  to  bottom,  and  more- 
over a  certain  poi'tion  of  the  intei-mediate  wall.  Of  that 
part  of  the  wall  which  is  now  called  the  curtain,  at  least 
one  half  was  visible  down  to  the  base  by  the  garrison  in 
the  tower  to  the  right,  and  the  other  half  by  the  garrison 
in  the  tower  to  the  left,  so  that  there  was  no  longer  any 
one  portion  of  the  wall  of  which  the  besieger  could 
approach  the  base,  without  exposing  himself  to  the 
direct  attack  of  the  besieged.  It  is  in  this  that  Jlaiding 
consists. 

The  invention  of  gunpowder  occasioned  deep-founded 


90  CARNOT. 

modifications   in  the   system  of  fortification,  as    to    the 
nature  of  attack  and  defence.     By  the  aid  of  this  inven- 
tion and  by  that  of  guns  of  various  kinds,  which  arose 
from  it,  the  besieger,  while  still  at  a  great  distance,  could 
breach  the  walls  by  his  artillery.     On  the  other  hand, 
the  besieged  gained  the  means  of  annoying  the  enemy 
long  before  he  had  reached  the  walls  by  his  covert  ways. 
Vast  banks  then  rested  against  the  walls,  on  which  the 
largest  guns  could  be  easily  worked.      Thence  arose  the 
necessity  of  giving  to  the  walls  thus  destined  an  immense 
and    expensive   thickness,    that   they   might   resist   the 
thrust  of  these  accumulations   of  earth.     They  at  the 
same  time  protected  the  outward  base  of  the  rampai'ts 
towards  the  open  country,  by  banks  ingenfously  contrived 
so  as  to  agree  with  the  undulations  of  the  ground.     By 
thus  defilading  the  ramparts,  they  deprived  the  besieger 
of  the  possibility  of  making  a  breach  from  afar ;  they 
obliged  him  to  approach  very  near  to  the  body  of  the 
place,  before  he  could  expect  much  effect  from  his  cannon 
against  the  walls  of  the  besieged  surmounted  with  guns. 
It  is  recounted  that  Soliman  II.  held  a  consultation 
with  his  generals,  relative  to  the  best  way  of  besieging 
Rhodes.     One   among  them,  an   experienced  man,  ex- 
plained   the    difficulties    of  the    enterprise.      The    only 
answer  the  Sultan  made  was  :    "  Advance  up  to  me,  but 
remember  that  if  thou  puttest  only  the  point  of  thy  foot 
on  the  carpet  in  the  midst  of  which  I  am  sitting,  thy 
head  shall  fall."     After  some   hesitation   the    Ottoman 
general  thought  best  to  raise  the  fearful  carpet,  and  roll 
it  on  itself,  in   proportion   as  he    advanced.     He    thus 
safely  got  closely  up  to  his  master,  who  then  exclaimed : 
"  I  have  now  nothing  further  to  teach  thee  ;  thou  know- 
est  the  art  of  besieging."     Such  is,  in  fact,  the  fi^ithful 


THE    PKOBLEM    OF    FORTIFICATION.  91 

image  of  the  first  movements  of  the  besieger,  who  wants 
to  get  possession  of  a  fortress  by  a  regular  attack.  The 
ground  represents  the  Sultan's  carpet.*  His  life  is 
endangered  unless  he  advances  under  cover ;  but  let 
him  dig  the  earth ;  let  him  heap  up  the  rubbish  in  front 
of  him  ;  let  him  unceasingly  roll  up  a  little  of  the  carpet 
as  he  advances  ;  and  behind  this  movable  shelter  the 
besiegers,  carrying  with  them  a  powerful  artillery,  ap- 
proach the  ramparts  of  a  fortress  very  soon  in  full  force, 
without  being  seen  by  the  besieged. 

The  problem  of  fortification  may,  indeed,  be  consid- 
ered at  bottom  as  a  particular  case  of  the  geometrical 
theory  of  polygonal  stars.  This  assemblage,  appai'ently 
so  inextricable,  of  salient  and  of  reentering  angles,  of 
bastions,  of  curtains,  of  demilunes  and  tenailles,  &c.,  of 
which  modern  fortresses  consist,  is  the  solution  of  the 
very  old  question  of  flanking.  We  may  in  some  points 
vary  the  construction,  but  the  aim  is  always  the  same. 
The  abstract  principles  of  the  art  have  become  clear  and 
evident.  The  illustrious  corps  of  officers  who  at  the 
present  day  ai'e  at  liberty  to  apply  them  to  the  defence 
of  the  country,  have  had  the  good  sense  to  abandon  the 
mystery  with  which  it  was  before  surrounded,  and  with 
which  it  has  been  so  severely  reproached.  Fortification 
is  taught  like  other  sciences  ;  it  is  founded  on  the  most 
elementary  geometry ;  a  mere  amateur  can  familiarize 
himself  with  the  theory  in  a  few  lessons. 

*  This  is  scarcely  a  "faithful  image,"  and  unless  the  story  could 
be  improved,  it  is  hardly  worth  preserving.  The  gradual  increase  of 
labour  and  cover  in  advancing,  and  the  total  absence  of  cover  at  the 
commencement,  are  features  foreign  to  a  regular  siege;  there  cover 
is  obtained  at  first,  and  they  go  steadily  on,  making  no  more  or  less 
than  the  requisite  cover  all  the  way.  The  story,  however,  might  be 
applied  to  an  old  fortress  with  very  lofty  towers,  which  would  require 
more  cover  as  you  got  nearer. —  Translator. 


92  CAKNOT. 

Let  us  now  remark,  that  modern  fortification  has  the 
defect  of  being  extremely  expensive.  It  was  this  ruin- 
ous defect  that  Carnot  wished  to  remove,  by  substituting 
curved  {or  vertical)  fire  for  the  direct.*  Carnot  sur- 
rounds a  fortress  by  a  simple  wall,  not  faced,  but  fur- 
nished with  scarp  and  counterscarp.  The  wall  does  not 
require  a  great  thickness,  because  it  has  not  to  resist  the 
thrust  of  the  earth  destined  to  bear  artillery  on  it.  Be- 
hind this  wall  he  places  mortars,  howitzers,  and  pierriers 
which  are  to  carry  curved  fire  into  the  country ;  the 
results  of  which,  according  to  him,  must  be  much  more 
eifective  than  those  of  direct  firing,  and  oppose  obstacles 
to  the  enemy's  advance,  more  and  more  efficacious  in 
proportion  to  his  ai)proach.  The  wall  is  defiladed  against 
the  direct  fire  of  the  besieger,  by  the  earthen  counter- 
scarp, forming  one  of  the  faces  of  the  ditch.  It  seems, 
then,  that  to  make  a  breach,  it  is  requisite,  as  in  the 
present  system  of  fortification,  to  crown  the  covered  Avay  ; 
an  operation  which,  according  to  the  author,  would  be 
eminently  galling  to  the  assailant.  This  supposes  that  a 
breach  could  not  be  made  in  Carnot's  wall  but  at  a  very 
short  distance,  and  within  le  tir  de  plein  fouet,  or  point- 
blank  range.  Foreign  experiments,  it  is  said,  contradict 
this  hypothesis ;  by  employing  curved  fire,  a  breach 
might  be  made  at  a  sufficiently  great  distance,  provided 
the  projectiles  were  of  very  large  calibre.  The  question 
then  is  not  yet  solved  ;  t    the  new  mode  prqiosed  by 

*  The  word  "curved  fire"  is  employed,  though  "vertical"  is  the 
usual  term  hi  English  technical  language,  because  curved  includes 
more— as  the  vertical,  the  ricochet,  and  every  thing  between  those 
two.  It  might  possibly  be  rendered"  elevated  fire;"  and  it  should 
be  remembered  that  Carnot  intended  to  use  a  sort  of  ricochet  fire  as 
well  as  tlie  vertical. —  Translator. 

■f  We  shorild  say,  the  question  is  now  solved;  the  experiments 
made  by ybj'ej^nei's  are  to  be  relied  on,  and  are  kept  on  record;  at 


THE    VERTICAL    FIRE.  93 

Carnot  seems  to  call  for  a  more  thorough  examination  ; 
but  meanwhile  we  must  applaud  our  illustrious  colleague 

least  that  part  which  he  speaks  of,  namely — the  impossibility  of 
breaching  Carnot's  wall  from  a  distance.  In  the  experiments  made 
at  Woolwich,  a  wall  well-built,  and  having  had  time  to  consolidate, 
icas  breached  with  expedition  and  certainty;  though  of  course  with  a 
very  large  expenditure  of  arnmunition,  on  account  of  the  uncertain 
nature  of  the  fire;  that  is,  throwing  heavy  shot  over  an  earthen 
bank,  down  against  the  wall  on  the  opposite  side.  The  vertical  fire 
question  does  not  admit  of  quite  so  easy  a  solution;  but  Carnot  cer- 
tainly miscalculated  the  efl'ect  of  the  very  small  balls  he  proposed  to 
shower  down,  as  is  immediately  evident  theoretically,  and  has  been 
tested  practicall}-.  He  said  that,  a  large  ball  fired  at  a  certain  angle 
with  a  certain  velocity,  being  found  to  penetrate  on  falling  into  hard 
earth,  about  its  own  diameter,  his  small  balls  fired  under  like  angles 
and  velocities  would  also  penetrate  to  the  amount  of  their  diameters; 
but  this  is  fallacious,  he  having  forgotten  the  resistance  of  the  air, 
which  retards  balls  of  different  sizes  in  the  proportion  of  the  sqtiares 
of  their  diameters,  wliile  their  force,  or  power  of  i-etaining  momentum, 
is  in  proportion  to  the  cubes  of  tlieir  diameters.  This  is  an  immense 
difference  when  it  is  recollected  that  Carnot's  given  experiment  was 
with  a  ball  of  some  five  or  six  inches  diameter,  while  those  he  pro- 
posed would  have  been  about  one  inch;  and  that  in  vertical  fire  this 
resistance  of  the  air  acts  on  the  ball  through  a  lengthened  route  both 
ascending  and  descending.  Experiment  with  the  proposed  balls  at 
Woolwich,  has  shown  that  the  wounds  inflicted  by  these  balls  would 
be  seldom  disabling,  unless  they  struck  a  man  on  the  head :  their 
force  being  only  somewhat  greater  than  the  strongest  effort  of  a 
strong  man.  It  has  also  been  shown,  that  they  are  given  to  scatter 
so  much,  that  the  outworks  in  the  neighbourhood  must  be  abandoned 
as  soon  as  this  fire  is  used  from  the  body  of  the  place;  in  fact,  by 
making  vertical  fire  the  whole  of  his  defence,  Carnot  forfeits  all  the 
time  which  the  use  of  direct  fire  used  to  cause  the  assailant  to  expend 
in  approaching  to  the  summit  of  the  covered  way,  as  a  very  slight 
application  of  raw  hides,  &c.,  supported  above  the  approaches,  would 
protect  the  assailants;  and  when  there,  the  neighbouring  works  could 
not  assist  in  defence,  as  they  must  be  abandoned  fi-om  the  scattering 
fire  from  the  body  of  the  place. 

Still  vertical  fire  is  often  good  and  effective,  especially 'in  the  latter 
parts  of  sieges;  and  all  writers  on  fortification  recommend  its  exten- 
sive use  both  in  defence  and  attack.    Its  use  has  been  restricted  by 


94  CARNOT. 

for  his  endeavour  to  render  the  means  of  defence  as 
efficacious  as  the  means  of  attack,  which  were  due  to  the 
genius  of  Vauban. 

PUBLICATION  OF  THE  TREATISE  ON  THE  DEFENCE  OF 
FORTRESSES. 

Napoleon  was  greatly  irritated  in  1809,  at  the  slight 
resistance  that  several  fortified  places  made  to  the  attacks 
of  the  enemy ;  and  therefore  he  caused  Carnot  to  be  asked, 
towards  the  end  of  that  year,  to  write  a  special  code  of 
instructions  on  this  important  branch  of  the  military  art, 
from  which  the  governors  of  citadels  might  learn  the  re- 
sponsibility of  their  functions,  and  the  full  extent  of  their 
duty.  In  this  mission  Carnot  saw  a  fresh  opportunity  of 
rendering  himself  useful  to  his  country,  and  did  not  hesi- 
tate to  accept  it,  although  his  health  then  occasioned  some 
serious  inquietude. 

In  the  eyes  of  the  Emperor,  perhaps  working  fast  was 
more  esteemed  than  working  tvell.  On  this  occasion, 
however,  his  hopes  did  not  go  so  far  as  to  imagine  that 
the  composition  of  a  considerable  work  that  might  re- 
quire ten  or  twelve  large  plates,  and  in  which  some  well- 
selected  historical  examples  should  accompany  and  sup- 
port the  precepts,  could  be  executed  in  less  than  a  year. 
Well,  Gentlemen,  four  months  scarcely  elapsed  from  the 
moment  that  Carnot  knew  Napoleon's  desire,  to  the  pub- 
lication of  the  celebrated  Treatise  on  the  Defence  of 
Fortresses. 

the  difficulty  of  transporting  ammunition,  or  the  train  being  Ijon-owcd 
from  ships,  or  its  being  incomplete;  but  the  advantage  is  allowed  by- 
all  writers,  though  only  as  a  part  of  the  system.  Carnot's  principal 
novelty  was  the  theory  of  mailing  it  take  the  place  of  every  thing  else ; 
and  that  theory  has  been  ably  demolished  by  the  practical  arguments 
of  Sir  Howard  Dousflas. —  Translator. 


GOVERNOR    OF    ANTWERP.  95 


CARNOT    AN    ACADEMICIAN. 

From  1807  to  1814  Carnot  had  lived  in  retirement; 
he  scrupulously  fulfilled  his  duties  as  an  academician. 
This  title  had  been  restored  to  him  the  5th  Germinal, 
year  VIII.,  after  the  decease  of  Le  Roy.  Nearly  all  the 
Memoirs  on  Mechanics  submitted  to  the  judgment  of  the 
First  Class  of  the  Institute,  were  referred  to  him.  His 
rare  sagacity,  with  luminous  clearness  and  remarkable 
precision,  pointed  out  and  characterized  the  new  and 
salient  portions.  I  could  cite  a  certain  author  on  ma- 
chines, who  did  not  fully  conceive  his  own  discovery, 
until  after  it  had  had  the  good  fortune  to  pass  through 
the  filter  of  that  learned  critic.  He  had,  besides,  a  sort 
of  merit  that  is  not  always  the  auxiliary  of  high  science : 
he  knew  when  to  doubt ;  to  his  eye  theoretical  results 
were  not  always  infallible. 

EVENTS  OF  1813. CARNOT  APPOINTED  TO  THE  COM- 
MAND AT  ANTWERP. 

We  have  now  reached  the  events  of  1813.  Carnot 
was  not  rich  enough  to  subscribe  to  the  newspapers. 
Every  day  at  the  same  hour,  we  see  him  come  to  the 
Library  of  the  Institute,  approach  the  fire,  and  read  with 
visible  anxiety  the  news  of  the  progress  of  our  enemies. 
On  the  24th  of  January,  1814,  the  interest  he  felt  ap- 
peared greater  than  ever  ;  he  asked  for  some  paper,  and 
as  fast  as  the  pen  could  trace,  wrote  the  following  letter, 
which  you  will  no  doubt  like  to  hear  read  : — 

"  Sire, — As  long  as  success  crowned  your  enterprises, 
I  abstained  from  offering  to  your  Majesty  services  which 
I  did  not  think  were  agreeable  to  you  ;  now,  that  ill-for- 
tune puts  your  constancy  to  a  severe  proof,  I  no  longer 


96  CARNOT. 

hesitate  to  offer  you  the  small  means  that  remain  to  me. 
It  is  little,  certainly,  to  offer  a  sexagenary  arm  ;  but  I 
have  thought  that  the  example  of  a  soldier  whose  patriotic 
sentiments  are  known,  might  rally  to  your  Eagles  many 
men  who  are  undecided  what  line  to  adopt,  and  who  may 
allow  themselves  to  be  persuaded,  that  in  abandoning 
them,  they  were  serving  their  country. 

"  There  is  still  time  for  }  ou.  Sire,  to  conquer  a  glorious 
peace,  and  to  have  the  love  of  the  great  people  restored  to 
you. — I  am,  &c."' 

The  details  that  I  have  thought  it  right  to  give  you, 
relative  to  the  circumstances  connected  with  the  writing 
of  this  letter,  will,  I  trust,  undeceive  those  who,  accus- 
tomed to  concentrate  all  their  affections  on  the  person  of 
Napoleon,  fancied  in  Carnot's  concluding  words,  a  cruel 
attack  from  the  old  democrat,  prepared  at  long-shot  dis- 
tance, against  the  man  who  had  confiscated  the  Republic 
to  his  own  advantage.  In  truth.  Gentlemen,  it  required 
a  man  to  be  very  determined  to  substitute  personal  ques- 
tions for  the  national  weal,  to  blame  the  illustrious  sexa- 
genarian's offer  to  defend  a  fortress,  when  otherwise  he 
had,  relative  to  capitulations,  not  long  since  resumed  his 
idea,  expressed  in  the  noble  words  of  the  famous  Blaise 
de  Montluc  to  Marshal  de  Brissac  :  /  would  rather  he 
dead  than  see  my  name  in  such  writings. 

Carnot  started  from  Paris  for  Antwerp  at  the  end  of 
January,  without  having  even  seen  the  Emperor.  It 
was  time.  Gentlemen,  for  the  new  governor  could  not 
reach  the  fortress  on  the  morning  of  the  2d  of  February, 
but  by  threading  the  enemy's  bivouacs.  The  bombard- 
ment of  the  town,  or  rather  the  bombardment  of  our  fleet, 
for  there  were  some  English  among  the  besiegers,  began 
the  next  day ;  it  lasted  throughout  the  day  of  the  3d, 


GOVERNOR    OF    ANTWERP.  97 

and  of  the  4th,  with  part  of  the  6th.  Fifteen  hundred 
bombs,  eight  hundred  cannon  balls,  many  red-hot  balls 
and  fusees,  Avere  thrown  on  our  ships.  Tlie  enemy  then 
retired  ;  the  experience  of  three  days  had  sutficed  to  give 
him  the  estimate  of  the  rough  tilter  he  had  to  deal  with. 
I  will  borrow  from  the  journal  of  tlie  siege  kept  by  M. 
Ransonnet,  Carnot's  aide-de  camp,  some  details  that  may 
1)6  interesting,  and  which  will  show  the  strictness  of  the 
man  and  of  the  times. 

On  the  10th  of  February,  the  new  governor  of  Ant- 
werp wrote  to  the  Mayor  of  the  town  : — 

"I  am  very  much  surprised  that  the  person  charged 
with  ordering  the  furnishing  of  my  quarters,  did  not  re- 
strict himself  to  what  was  necessar3^ 

"  I  also  desire  that  any  demands  of  this  nature,  made 
on  my  account,  may  not  have  the  cliaracter  of  a  forced 
requisition. 

"All  the  effects  enumerated  in  the  annexed  list  are 
unnecessary." 

The  necessities  of  the  Belgian  campaign,  having  sug- 
gested to  the  Emperor  the  idea  of  borrowing  some  troops 
from  the  garrison  of  Antwerp  for  the  army,  Carnot  wrote 
a  despatch  to  the  General-in-Chief,  Maison,  dated  the 
27th  of  March,  whence  I  have  extracted  the  following 
passages  : — 

"  In  obeying  the  orders  of  the  Emperor,  I  am  obliged 
to  declare  to  you,  the  Commander-in-Chief,  that  these 
orders  are  equivalent  to  ordering  Antwerp  to  be  ceded 
....  The  circumference  of  this  place  is  immense,  and 
there  would  be  at  least  fifteen  tliousand  good  troops  re- 
quired to  defend  it.  How  could  His  Majesty  suppose 
that  with  three  thousand  sailors,  the  greater  part  of  whom 

SEC.    SER.  5 


98  CARNOT. 

have  never  seen  fire,  I  could  keep'the  fortress  of  Antwerp 
with  the  eiglit  dependent  forts  ?  .  .  .  . 

"  It  only  remains  then  here,  for  us  to  disgrace  ourselves 
or  to  die  ;  I  beg  you  to  be  believe  that  we  are  all  deter- 
mined to  prefer  the  latter  .... 

"  I  think,  Sir,  that  if  you  could  take  upon  yourself  to 
leave  me  at  least  the  infantiy  and  the  artillery  (there  was 
at  Antwerp  a  detachment  of  the  Imperial  Guard),  you 
will  render  a  very  great  service  to  His  JNIajesty ;  but  all 
will  be  ready  to  depart  to-morrow,  unless  I  receive  a 
counter-order  from  you,  whicli  I  shall  await  with  the 
greatest  impatience  and  the  greatest  anxiety." 

Besides  the  despatch  to  General  Maison,  I  find  under 
the  same  date  a  letter  to  the  Minister  of  War,  the  Duke 
de  Feltre  ;  and  I  i-emark  the  following  passage  in  it : — 

"  When  I  offered  to  serve  His  Majesty,  I  was  willing 
to  sacrifice  my  life  to  him,  but  not  my  honour.  Your 
Grace  knows  that  I  am  not  in  the  habit  of  dissimulating 
the  truth,  because  I  do  not  seek  favour.  The  truth  is, 
that  the  state  to  which  your  orders  reduce  me,  is  a  hun- 
dred times  worse  than  death,  because  I  have  no  chance 
of  saving  the  place  confided  to  me,  but  in  the  cowardice 
of  my  enemies." 

Bernadotte  having  wished  to  dissuade  Carnot  from  the 
line  of  conduct  that  he  had  laid  down  for  himself,  received 
from  him  the  following  answer  : — 

"  lOth  April,  1814. 

"  PpaNCE, — It  is  in  the  name  of  the  French  Govern- 
ment that  I  command  in  the  fortress  of  Antwerp.  That 
Government  alone  has  the  right  to  fix  the  termination  of 
my  duties  :  as  soon  as  it  shall  be  incontestably  established 
on  a  new  basis,  I  shall  hasten  to  obey  its  orders.  This 
resolution  cannot  fail  of  obtaining  the  approbation  of  a 


GOVERNOR    OF    ANTWERP.  99 

Prince  born  a  FrencliRian,  and  who  knows  so  well  the 
laws  prescribed  by  honour." 

After  the  events  of  Paris,  after  the  institution  of  a  Pro- 
visional Government,  the  Minister  of  War,  Dupont,  sent 
one  of  his  aides-de-camp  to  Antwerp.  The  following  is 
the  letter  that  Carnot  wrote  to  him  on  this  occasion  : — 

"  15th  April,  1814. 
"  I  must  acknowledge,  my  Lord  Count,  that  your  hav- 
ing sent  me  an  aide-de-camp  with  a  white  cockade  is  a 
calamity  :  some  wished  to  adopt  it  instantly,  others  have 
sworn  to  defend  Bonaparte  ;  a  sanguinary  conflict  would 
have  immediately  resulted  in  Antwei'p  itself,  if,  with  the 
advice  of  my  Council,  I  had  not  determined  to  defer  my 
adhesion,  and  that  of  all  the  armed  force  ....  Is  civil 
war  then  .wished  for  ?  is  it  wished  that  the  enemy  should 
become  master  of  all  our  strongholds  ?  and  because  the 
city  of  Paris  has  been  forced  to  accept  the  rule  of  the 
conqueror,  that  tlierefore  all  France  shall  receive  it  ?  It 
is  evident  that  the  Provisional  Government  is  only  trans- 
mitting the  orders  of  the  Emjieror  of  Russia.  Who  will 
ever  absolve  us  from  having  obeyed  such  orders  .''  What ! 
you  do  not  allow  us  even  to  preserve  our  honour ;  you 
yourself  become  an  accomplice  of  desertion,  promoter  of 
the  most  monstrous  anarchy!  The  lessons  of  1792  and 
1793  are  lost  upon  the  new  chiefs  of  the  State.  They 
first  seek  to  catch  our  adhesion  by  surprise,  by  affirming 
to  us  that  Napoleon  had  abdicated,  and  now  they  contra- 
dict it.  After  having  given  us  a  tyrant  instead  of  anar- 
chy, they  put  anarchy  in  place  of  the  tyrant.  When 
shall  we  see  the  end  of  these  cruel  oscillations  ?  Paris 
is  enjoying  only  a  momentary  peace  ;  a  perfidious  calm 
which  presages  to  us  the  most  horrible  tempests.     Oh, 


]  00  CARNOT. 

afflicting  and  withering  days,  bappy  those  who  have  not 
witnessed  you  ! " 

The  sentiments  with  which  Carnot  was  able  to  inspire  • 
the  population  of  Antwerp  are  known  to  the  whole  world. 
I  cannot  resist  the  pleasure,  however,  of"  citing  at  least 
some  passages  from  a  letter  that  was  delivered  to  him 
the  day  he  departed  for  Paris ;  after  having  been  thus 
ordered  by  the  government  under  the  elder  branch  of  the 
Bourbons,  who  had  remounted  the  throne.  The  authori- 
ties and  inhabitants  of  the  suburb  of  Borgerhout,  the  de- 
struction of  which  had  been  resolved  on,  but  which  he 
thought  he  could  preserve  without  detriment  to  the  gen- 
eral defence,  thus  expressed  themselves  : — 

"  You  are  going  to  quit  us  ;  we  feel  deeply  afflicted  by 
it ;  we  would  wish  to  possess  you  still  a  little  longer ;  we 
solicit  this  great  favour  most  earnestly The  in- 
habitants of  Saint  Willebrord  and  of  Borgerhout  request 
permission  to  inquire  once  a  year,  of  the  person  who  may 
be  appointed  to  govern  them,  after  the  health  of  General 

Carnot AVe  may,  perhaps,  never  see  you  again. 

If  some  day  General  Carnot  allows  his  portrait  to  be 
painted,  and  would  permit  a  copy  of  it  to  be  made  for  us 

this  precious  present  would  be  deposited  in  the 

church  of  Saint  Willebrord." 

I  will  not  commit  the  fault,  Gentlemen,  of  weakening 
such  naive  and  touching  expressions  by  a  cold  commen- 
tary. 

CONDUCT  OF  CARNOT  DURING  THE  HUNDRED  DAYS. 

The  conduct  of  Carnot  during  the  Hundred  Days, 
appears  to  me  to  have  been  well  and  honoui-ably  epito- 
mized  in    those    memorable   words    that    Napoleon    ad- 


THE    HUNDRED    DATS.  101 

dressed  to  him,  after  the  battle  of  Waterloo  :    "  Carnot, 

I  HAVE  KNOWN  YOU  TOO  LATE  !  " 

But,  as  I  am  writing  a  biography  and  not  a  panegyric, 
I  will  frankly  say  that  Carnot,  as  member  of  the  Pro- 
visional Government  of  that  epoch,  laboured  under  the 
injurious  and  anti-national  influence  of  the  Duke  of 
Otranto,  which  led  him  to  give  his  adhesion  to  measures 
that  were  stamped  with  evident  feebleness,  and  to  others 
over  which  every  heart  animated  by  patriotic  sentiments 
would  gladly  throw  a  thick  veil. 

And  yet,  can  we  very  warmly  reproach  Carnot  with 
having  allowed  himself  to  be  fascinated  by  the  intrigues 
of  Fouche,  when  we  see  Napoleon,  notwithstanding  the 
strongest  suspicions  of  treason,  retain  that  man  in  his 
Council  ? 

Amidst  the  reproaches  ostensibly  addressed  to  Carnot, 
respecting  that  period  of  our  annals,  there  is  one  ou 
which  I  can  give  some  personal  explanation.  I  have 
heard  the  austere  Conventional  severely  blamed  for 
having  accepted  the  title  of  Count  of  the  Empire  ;  hap- 
pily my  memory  can  faitlifully  repeat  some  words  of  our 
colleague's  which  clear  up  this  point  in  his  life,  and  which 
were  related  to  me  by  an  officer  the  very  day  that  he 
heard  them. 

They  were  at  table,  at  the  Minister  of  the  Interior's 
house.  A  letter  arrives ;  the  minister  breaks  the  seal, 
and  almost  instantly  exclaims  :  "  AVell,  Gentlemen,  see 
me  here  a  Count  of  the  Empire  !  I  can,  however,  easily 
guess  whence  the  blow  comes.  It  is  my  dismissal  that  is 
wished  for,  that  is  demanded ;  I  will  not  give  him  that 
satisfaction  ;  I  will  remain,  because  I  tliink  I  can  be 
useful  to  my  country.  The  day  will  come,  I  hope,  when 
I  shall  be  allowed  to  explain  myself  fully  respecting  this 


102  CARNOT. 

perfidy  ;  at  present,  I  will  content  myself  with  disdaining 
this  vain  title,  with  never  annexing  it  to  my  name,  and 
especially  with  never  accepting  the  diploma,  however 
much  I  may  be  pressed  to  do  it.  From  this  moment,  Gen- 
tlemen, you  may  rest  assured  that  Carnot  will  not  long 
remain  Minister  after  our  enemies  have  been  repulsed." 

I  must  have  made  you  ill-appreciate  our  colleague, 
Gentlemen,  if  these  words  had  appeared  to  require  far- 
ther explanation. 

CARNOT    IN    EXILE. HIS    DEATH. 

Of  all  the  ministers  of  the  Hundred  Days,  Carnot  was 
the  only  one  whose  name  apeared  on  the  list  of  pro- 
scription prepared  on  the  24th  of  July,  1815,  by  the 
second  Restoration.  Whether  this  special  rigour  was 
the  consequence  of  the  patriotic  ardour  with  which  our 
colleague  disputed  with  foreigners  the  last  remnants  of 
the  French  territory,  or  of  his  persisting  (though  unfor- 
tunately without  good  result)  to  point  out  to  the  Empe- 
ror the  traitor,  who,  under  the  favour  of  his  former 
reputation  for  talent,  had  insinuated  himself  into  the 
Ministry,  still  his  glory  will  not  be  tarnished  by  it. 

Already,  on  the  evening  of  the  24th  July,  Carnot  had 
received  a  passport  from  the  Emperor  Alexander.  He 
used  it,  however,  only  in  Germany.  Obliged  to  travel 
under  a  feigned  name,  he  would  not  forego  the  title  of  a 
Frenchman  as  long  as  he  could  avoid  it.  It  was  there- 
fore again  as  a  Frenchman  that  he  traversed  the  great 
river  in  a  melancholy  mood,  to  the  very  banks  of  which 
he  had  had  the  supreme  honour  of  extending  our  fron- 
tiers, and  he  went  to  Warsaw. 

In  a  certain  country  not  far  from  ours,  a  stranger  is 
always   received   with    this    matter-of-course    formula  : 


HIS    EXILE    AND    DEATH.  103 

"  My  house,  and  all  that  it  contains  are  yours  ; "  but  at 
the  same  moment,  I  must  acknowledge,  it  is  not  rare, 
through  a  signal  that  the  servants  perfectly  well  under- 
stand, for  the  su^jposed  new  proprietor  to  be  ever  after 
shown  the  door  of  the  habitation  so  liberally  offered  to 
him.  The  reception  of  Carnot  in  Poland,  however, 
must  not  be  included  in  this  category.  Our  excellent 
friends,  the  brave  Poles,  did  not  confine  themselves  to 
mere  forms  of  politeness  towards  the  illustrious  exile. 
General  Krasinski  made  over  to  him  a  mayoralty  in 
land  of  8,000  francs  per  annum,  that  he  held  from  Na- 
poleon ;  the  Count  de  Pa9  wished  him  to  accept  the  pos- 
session of  several  domains.  Although  Carnot  was  not  a 
Freemason,  all  the  Masonic  Lodges  of  the  kingdom 
joined  in  a  subscription  that  produced  a  considerable 
sum  ;  finally,  and  of  all  these  offers  that  he  refused,  the 
following  w^ent  most  directly  to  the  heart  of  Carnot ;  a 
Frenchman,  poor  himself,  established  at  Warsaw  for 
many  years,  went  to  him  one  morning,  carrying  a  bag 
with  the  savings  of  his  whole  life  ! 

The  severity  of  the  Polish  climate,  the  wish  to  be 
nearer  to  France,  determined  our  colleague  to  accept  the 
kind  offers  of  the  Prussian  Government ;  he  settled  at 
Magdebourg,  where  he  passed  his  latter  years  in  study, 
in  meditation,  and  in  the  company  of  one  of  his  sons, 
whose  education  he  superintended.  It  was.  Gentlemen, 
a  fine  spectacle  to  see  the  whole  of  Europe,  above  all  to 
see  the  absolute  monarchs,  forced  in  some  measure  to 
render  homage  to  one  of  the  greatest,  most  noble,  most 
striking  men  in  the  French  Revolution  ;  even  to  one  of 
the  judges  of  Louis  XVI.,  even  to  a  member  of  the 
Committee  of  Public  Safety. 

Carnot  died  at  Magdebourg,  the  2d  of  August,  1823, 
aged  70  years. 


104  CAKNOT. 

PORTRAIT  OF    CARNOT. ANECDOTES    RELATIVE  TO  H^S 

POLITICAL    AND    PRIVATE    LIFE. 

If  iconographii  is  not  now  considered  by  anybody  as  a 
futile  science,  if  some  very  distinguished  minds  have 
made  it  the  object  of  their  earnest  study,  it  may  be  per- 
mitted me  here  to  say,  that  Carnot  was  of  tall  stature,  of 
manly  and  regular  features,  a  wide  and  calm  forehead, 
lively  and  penetrating  blue  eyes,  a  polite  demeanour, 
but  circumspect  and  cold  ;  that  at  the  age  of  sixty,  there 
was  still  perceptible  in  him,  even  in  a  civilian's  costume, 
something  of  the  military  air  to  which  he  had  been 
accustomed  in  his  youth. 

I  have  considered  him  in  all  his  phases, — as  a  mem- 
ber of  the  Conventional  Government,  of  the  Committee 
of  Public  Safety,  of  the  Executive  Directory,  the  Min- 
ister of  War.  a  Military  Engineer,  the  Exile,  the  Acade- 
mician. Still,  many  essential  traits  would  be  wanting  to 
the  portrait,  however  comprehensive  it  be  already,  if  1 
did  not  also  speak  of  the  private  man.  I  shall  not 
swer\e,  in  this  latter  portion  of  my  picture,  from  the 
style  that  I  adopted  in  the  beginning  ;  I  shall  advance 
always  proof  in  hand.  It  is  thus  I  think  that  a  geometer 
should  be  praised ;  I  mistake,  it  is  thus  that  everybody 
should  be  praised ;  seeing  how  rare  honour,  disinterest- 
edness, and  true  patriotism  are  among  the  living ;  and 
how  common,  on  the  contrary,  among  the  dead,  accord- 
in<T  to  their  funeral  eulogies  and  their  epitaphs  ;  the 
public  has  come  lo  the  wise  conclusion  of  no  longer 
believing  either  the  one  or  the  other. 

I  have  read  somewhere  that  Carnot  was  an  ambitious 
man.  I  will  not  stop  to  combat  this  opinion  in  form, 
but  I  will  relate,  and  you  yourselves  shall  judge. 


HIS    POLITICAL    AND    PRIVATE    LIFE.  105 

The  member  of  the  Committee  of  Pubhc  Safety,  who, 
in  1793,  organized  the  fourteen  armies  of  the  Republic, 
who  arranged  all  their  movements,  who  named  and 
appointed  generals,  who,  at  need,  as  at  Wattignies,  de- 
graded them  during  the  battle  under  the  enemy's  can- 
non,— was  only  a  Captain  of  Engineers. 

And  later,  when  the  Council  of  the  Five  Hundred, 
and  the  Council  of  the  Elders  of  the  Kepublic  of  the 
year  III.,  unanimously  called  Carnot  to  the  Executive 
Directory ;  when  having  again  become  the  supreme 
arbiter  of  our  militaiy  operations,  he  sent  Hoche  to 
la  Vendee,  Jourdan  to  the  Meuse,  and  Moreau  to  the 
Rhine,  instead  of  Pichegru  ;  when,  by  the  most  fortu- 
nate inspiration,  he  confided  the  command  of  the  army 
of  Italy  to  Bonaparte,  our  colleague  gained  a  step,  but 
only  one  step ;  he  had  become  chef  de  bataillon  hy 
seniority  ! 

Carnot  still  held  only  this  humble  rank,  when  the 
coup  d'etat  of  the  18th  Fructidor  banished  him  from 
France. 

The  extremely  hierarchical  ideas  of  the  First  Consul 
could  never  have  reconciled  themselves  to  a  mere  chef 
de  bataillon  being  Minister  of  War.  Wherefore  in  the 
year  IX.,  he  did  not  elevate  Carnot  to  that  eminent  post 
until  after  he  had  named  him  Inspector  General  of 
Reviews.  Still,  it  was  only  turning  the  obstacle  aside, 
instead  of  removing  it.  The  semi-military,  semi-civil, 
grade  of  Inspector  General  of  Reviews,  did  not  prevent 
the  Minister  of  War,  under  the  government  of  the  Con- 
suls, frojn  being  a  simple  chef  de  bataillon  in  the  Corps 
of  Engineers. 

Carnot  quitted  the  Ministry  the  16th  Vendemiaire, 
year  IX.     Twelve  days  after,  liis  successor  asked  for  the 

5* 


106  CARNOT. 

illustrious  citizen's  name  to  be  inserted  in  the  list  about 
to  be  i'ormed  of  tlie  Genei-als  of  Division  of  the  French 
army.  The  Report  recalled  in  appropriate  terms,  and 
even  Avith  a  degree  of  vivacity,  all  that  our  colleague  had 
done  for  the  national  glory  and  independence.  The 
Minister  went,  even  in  tiie  name  of  justice,  of  esteem  and 
oi friendship,  to  invoke  the  magnanimity  of  the  Consuls ; 
the  magnanimity  was  at  fault ;  they  did  not  answer  the 
Report,  and  the  dismissed  Minister  remained  in  his  old 
rank. 

When  it  was  requisite,  in  1814,  to  send  orders  to  the 
new  Governor  of  Antwerp,  the  clerks  of  the  War-office, 
in  order  to  write  the  address,  sought  for  the  official  titles 
of  Carnot  in  the  Army-list,  and  were  astounded  at  seeing 
that  the  Emperor  had,  without  considering  it,  placed  a 
chef  de  bataillon  at  the  head  of  a  crowd  of  old  generals. 
The  service  would  evidently  have  suft'ered  from  such  a 
state  of  things  ;  the  necessity  of  remedying  it  was  at 
once  felt,  and,  in  imitation  of  a  certain  ecclesiastical  per- 
sonage, who  in  the  same  day  received  the  minor  orders, 
the  major  orders,  priesthood,  and  episcopacy,  our  col- 
league, in  a  few  minutes,  passed  through  the  various 
grades  of  lieutenant-colonel,  colonel,  brigadier-general, 
and  general  of  division. 

Yes,  Gentlemen,  Carnot  had  ambition  ;  but,  as  he  said 
himself,  it  was  the  ambition  of  the  three  hundred  Spartans 
going  to  defend  Thermopyl(B  ! 

The  man  who,  in  an  all-powerful  position,  had  never 
thought  of  making  himself  the  equal  of  those  whose  vast 
operations  he  was  directing,  also  disdained  the  gifts  of 
fortune.  When  he  returned  to  private  life,  his  small 
patrimony  was  scarcely  intact.  How  is  it,  with  the  most 
simple  tastes,  with  a  strong  antipathy  for  pageantry  and 


HIS    STRICT    HONESTY.  107 

show,  that  Carnot  even  unintentionally  does  not  reach,  if 
not  riches,  at  least  the  easy  circumstances  of  those  men 
who,  like  him,  have  long  held  brilliant  employments  ? 
Some  facts  will  serve  as  answers. 

After  the  18th  Bruraaire,  at  the  moment  when  Carnot 
became  Minister  of  War,  the  pay  of  the  troops,  and,  what 
must  occasion  still  more  surprise,  the  pay  of  the  clerks, 
was  fifteen  months  in  arrear.  A  few  weeks  elapsed  and 
all  was  paid  up  ;  all,  except  the  salary  of  the  Minister 
himself ! 

Pins,  was  the  name  given  to  a  sort  of  gratuity  destined 
in  appearance  for  the  wife  of  any  one  with  whom  a  farmer, 
a  merchant,  or  a  commissary  had  concluded  a  contract, 
whether  public  or  private.  Although  pins  did  not  appear 
in  the  written  conditions,  the  contracting  parties  did  not 
therefore  regard  them  as  less  obligatory  ;  habit,  tliat  sec- 
ond nature,  had  at  last  come  to  acknowledge  them  as 
legal ;  the  most  sensitive  consciences  satisfied  themselves 
by  not  fixing  their  amount. 

A  horse-dealer,  whose  offer  Carnot  had  approved,  was 
going,  according  to  custom,  to  bring  him  a  considerable 
sura,  under  the  name  of  pins  ;  it  was,  I  believe,  50,000 
francs.  The  Minister,  at  first,  does  not  understand.  At 
the  Committee  of  Public  Safety,  where  he  had  served  his 
apprenticeship,  the  purveyors  took  good  care  not  to  speak 
of  pins.  All  is  explained  at  last,  and  Carnot,  far  from 
being  angry,  receives  with  a  laugh  the  notes  that  are  pre- 
sented to  him  ;  he  receives  them  with  one  hand,  and  gives 
them  back  with  the  other,  as  a  first  instalment  of  the 
price  of  the  horses  that  the  dealer  had  agreed  to  furnish 
for  our  cavalry,  and  demands  an  immediate  receipt. 

In  the  most  violent  paroxysms  of  their  fury,  the  fac- 
tions had  the  prudence  not  to  attack  Carnot  as  a  private 


108  CARNOT. 

man  ;  never  did  their  unhallowed  breath  try  to  tarnish 
the  virtues  of  the  son,  of  the  husband,  or  of  the  father  ; 
as  to  disinterestedness  especially,  both  friends  and  ene- 
mies were  always  agreed.  I  might  therefore  on  this 
point  remain  content  with  the  two  instances  I  have  given. 
There  is  another,  however,  which  it  is  desirable  to  rescue 
from  oblivion  ;  the  memory  of  Carnot  does  not  require  it, 
but  I  have  a  slight  hope  that,  by  being  reminded  of  it, 
some  ministers  may  feel  arrested  in  their  prodigalities, 
and  certain  parties  from  indulging  their  avarice  ! 

After  the  18th  Brumaire,  the  projected  operations  for 
the  army  of  reserve  imperiously  required  that  Moreau 
should  without  delay  send  one  of  his  divisions  to  the 
army  of  Italy.  The  direct  intervention  of  the  Minister 
of  War  did  not  appear  too  much  to  carry  so  important  a 
negotiation  to  a  successful  conclusion.  In  execution  of 
an  order  of  the  Consuls,  of  the  15tli  Floreal,  year  VIII., 
Carnot,  accompanied  by  six  officers  of  the  staff,  two  cou- 
riers, and  one  servant,  went  to  Germany.  On  the  route 
be  inspected  the  troops  echelonnees  between  Dijon  and 
Geneva  ;  he  then  traversed  the  cantonments  of  the  Rhine, 
visited  the  fortresses,  arranged  with  the  Commander-in- 
Chief  the  plan  for  the  next  campaign,  and  returned  to 
Paris.  The  Treasury  had  given  him  24,000  francs.  On 
his  return,  he  restored  10,680  francs.  He  was  so  fearful 
that  the  expenditure  of  13,320  francs,  (or  £550,)  for  ten 
persons  making  a  long  journey  should  appear  too  much, 
that  he  sent  in  a  detailed  report,  excusing  himself  as  if 
he  had  been  prodigal.  The  following  was  his  letter  to 
the  Consuls  :  "  You  will  have  the  goodness  to  remark 
that  you  have  desired  me  to  give  some  eclat  to  my  mis- 
sion ;  that  in  the  principal  places  I  was  obliged,  accord- 
ing to  your  orders,  to  assume  a  certain  appearance  ;  in 


LATOUK    d'aUVERGNE.  109 

short,  that  it  was  requisite,  from  the  character  of  gener- 
osity with  which  you  ai'e  animated,  that  I  should  allow 
some  gratification  to  my  companions  in  travel  and  in 
fati"-ue  ! "  Be  pleased  to  remember.  Gentlemen,  that  the 
journey,  the  eclat,  the  gratifications  amounted  altogether 
to  13,320  francs  ;  do  not  forget  that  it  was  one  of  the 
ministers,  inspecting  armies  who  was  going  to  decide  on 
the  fate  of  his  country,  who  spoke  thus,  and  you  will 
agree  with  me,  I  think,  that  if  the  world  is  improving,  it 
is  not  in  economy. 

The  Treasury  did  not  know  under  what  form  to  record 
the  10,G80  francs  returned  by  Carnot  ;  but  it  was  not  the 
first  essay  on  the  part  of  our  colleague  :  by  searching 
back  to  the  epochs  when  he  inspected  the  Republican 
armies,  as  representative  of  the  people,  the  Clerks  of 
Finance  found  in  their  registers  the  forms  they  sought, 
and  these  occurred  as  often  as  Carnot  had  executed  simi- 
lar missions. 

The  name  of  Carnot  would  still  present  itself  to  my 
mind  if,  after  so  many  instances  furnished  by  history  in 
all  countries,  it  were  yet  required  to  prove  that  an  ardent 
mind  can  be  allied  to  cold  and  reserved  manners.  Un- 
doubtedly, no  one  ever  had  a  right  to  say  of  him,  as 
D'Alembert  said  of  one  of  the  old  secretaries  of  our 
Academy  :  He  is  a  volcano  covered  with  snow  ;  but  I 
may  be  allowed  to  show  at  least,  that  our  colleague's  con- 
ceptions often  had  a  certain  something  in  them  that  went 
direct  to  the  heart,  touching,  moving,  electrifying  ;  some- 
thing, in  short,  stamped  with  an  indefinable  seal,  never 
borne  by  the  works  of  heartless  men,  of  men  whose  facul- 
ties have  no  concentration  of  mind.  Two  more  citations, 
and  my  thesis  will  be  proved. 

Latour  of  Auvergne,  born  of  the  Turenne  family,  did 


110  CARNOT, 

not  even  express  regret  at  losing  bis  advantageous  posi- 
tion througli  the  breaking  out  of  the  Revolution  ;  but  when 
the  enemy  menaced  our  frontiers,  it  was  to  the  frontiers 
that  he  was  seen  to  march.  Modesty  made  him  decline 
all  promotion  ;  the  old  captain  obstinately  remains  a  cap- 
tain. In  order  not  to  deprive  the  country  of  the  eminent 
services  that  Monsieur  Latour  d'Auvergne  could  render 
it,  Carnot  authorizes  the  representatives  of  the  people  to 
group  together  all  the  companies  of  Grenadiers  of  the 
army  of  the  Western  Pj'renees,  and  form  a  separate 
corps  of  them  ;  never  to  place  a  senior  oflRcer  over  them, 
and  to  remove  witli  equal  care  all  the  captains  that  were 
senior  to  Latour  d'Auvergne  ;  by  this  arrangement  the 
diffident  officer  finds  himself  daily  in  charge  of  an  impor- 
tant command.  The  name  of  infernal  column  given  by 
the  Spaniards  to  this  body  of  troops  soon  sanctions  in  a 
splendid  way  all  that  there  was  of  anomalous,  of  unusual, 
and  strange  in  the  contrivance  suggested  by  Carnot,  and 
carried  into  effisct  by  the  representatives. 

Latour  d'Auvergne,  whom  you  now  know,  Gentlemen, 
as  a  military  man,  for  the  third  time  quitted  his  retreat 
and  his  beloved  learned  studies,  and  asked  to  serve  under 
Moreau,  when  Carnot  became  Minister  of  War  after  the 
18th  Brumaire.  Already  at  that  epoch  the  First  Consul 
would  not  certainly  have  approved  an  arrangement  simi- 
lar to  the  one  that  the  Conventional  representatives 
adopted  in  the  Pyrenees.  Carnot,  however,  sulFered  in 
seeing  that  the  chief  of  the  infernal  column,  he  who 
counted  so  many  dashing  services,  that  the  estimable 
author  of  the  Gaulish  Origins — must  w^e  add,  that  a 
correspondent  of  the  Institute,  should  arrive  on  the  banks 
of  the  Rhine  as  an  obscure  officer.  The  title  of  First 
Grenadier  of  France   strikes    his   imagination  ;   Latour 


LATOUR    d'AUVERGNE.  Ill 

d'Auvergne  is  invested  witli  it  by  an  official  act ;  and 
from  that  moment,  without  quitting  his  Grenadier  epau- 
lettes, he  became,  in  the  eyes  of  the  soldiers,  the  equal 
if  not  the  superior  of  all  the  dignitaries  in  the  army. 

The  First  Grenadier  of  France  was  killed  by  a  lance 
the  27th  of  June,  1800,  at  the  battle  of  Neubourg.  The 
army,  the  whole  of  France,  wept  bitterly  over  this  loss. 
As  for  Carnot,  his  deep  grief  inspired  him  with  an  idea 
that  the  ancients,  otherwise  so  idolatrous  of  military 
glory,  might  envy  us.  By  an  order  emanating  from 
Carnot,  when  the  4Gth  demi-brigade  was  mustered,  the 
name  of  Latour  d'Auvergne  was  always  called  out  as 
the  first  on  tlie  roll.  The  grenadier  placed  at  the  head 
of  the  first  rank  then  advanced  two  steps,  and  answered 
in  a  tone  to  be  heard  all  along  the  line — Died  on  the  field 
of  honour. 

The  brief,  expressive,  solemn  homage  that  a  regiment 
thus  daily  paid  to  him  who  had  rendered  himself  illustri- 
ous in  its  ranks  by  courage,  knowledge,  and  patriotism, 
must,  I  think,  continue  that  excitement  which  produces 
heroes.  I  assert,  at  all  events,  that  the  noble  words  of 
Carnot,  repeated  in  the  chamber,  in  the  guard-room,  un- 
der the  tent,  in  the  bivouac,  had  thoroughly  preserved  the 
remembrance  of  Latour  d'Auvergne  in  the  memory  of 
our  soldiers.  "  Where  are  those  long  files  of  grenadiers 
going  ?  "  exclaimed  the  aide-de-camp  of  Marshal  Oudinot, 
when,  in  the  beginning  of  Vendemaire,  year  XIV.  (Octo- 
ber, 1805),  the  avant  garde  of  the  great  army  passed 
through  Neubourg.  "  Why  are  they  swerving  from  the 
route  laid  down  for  them  ?  "  Their  silent  and  grave 
march  awakened  curiosity  ;  they  are  followed,  they  are 
observed.  The  grenadiers  were  going,  Gentlemen,  near 
Oberhausen,  thoughtfully  to  pass  their  sabres  over  the 


112  CARNOT. 

rough  block  of  stone  that  covered  the  body  of  the  first 
Grenadier  of  France. 

I  return  thanks,  Gentlemen,  to  M.  de  Savary,  the  ven- 
erable old  man,  who,  a  witness  of  the  touching  scene  near 
Oberhausen,  has  allowed  me  to  draw  it  from  oblivion,  and 
thus  to  unite  in  one  mutual  sentiment,  the  admirable 
army  of  Austerlitz  with  the  admirable  armies  of  the  Re- 
public. I  am  happy  also,  that  names  which  are  dear  to 
you,  that  the  names  of  two  of  our  old  colleagues,  that  the 
names  of  Latour  d'Auvergne  and  of  Carnot,  happen  to 
occupy  so  noble  a  place  in  this  patriotic  reminiscence  ! 

Great  employments,  like  great  heights,  usually  occasion 
a  vertigo  in  the  heads  of  those  Avho  reach  them  suddenly. 
This  man  thinks  that  by  pageantry  and  prodigality  he 
ought  to  make  people  forget  the  years  he  has  passed  in 
mediocrity  and  constraint.  That  man  becomes  disdainful 
and  insolent,  harsh  and  churlish,  and  thus  revenges  him- 
self on  the  unfortunate  i^eople  who  have  now  to  solicit 
him,  for  the  disdain,  the  arrogance,  the  brutality  that  he 
had  to  undergo  Avhen  he  had  to  solicit  them.  A  crowd  of 
names  of  individuals  suggest  themselves  to  fill  up  this 
sketch,  in  case  any  one  should  dispute  its  fidelity.  Do 
not  suppose,  however,  that  by  passing  over  some  mush- 
rooms so  lightly,  I  intend  to  constitute  myself  the  advo- 
cate of  privilege ;  I  wish  to  prove,  on  the  contrary,  by 
the  example  of  Carnot,  that  minds  of  a  certain  tempera- 
ment can  resist  contagion. 

Six  months  after  the  coup  d'etat,  on  the  18th  Fructi- 
dor,  Carnot  is  otficially  accused  to  the  Council  of  the 
Five  Hundred  of  having  had  frequent  and  intimate  com- 
munications with  Pichegru,  at  a  time  when  that  general, 
a  member  of  the  Legislative  Body,  soiled  his  brilliant 
military  reputation  by  his  intrigues.     Carnot  denies  such 


COLONEL    BISSON.  113 

communications.  He  proves,  besides,  that  he  could  not 
have  had  "secret  interviews  at  his  house.  He  added  : 
"I  feel  that  people  will  say  if  it  was  not  at  your  house  it 
was  elsewhere.  "Well,  I  declare,  that  during  all  the  dura- 
tion of  my  directorial  functions,  I  have  not  gone  out  twelve 
times  "without  being  accompanied  by  my  wife,  my  sisters, 
or  my  children  !  " 

It  is  possible,  Gentlemen,  that  in  France,  that  else- 
where, men  in  power  may  have  had  this  simplicity  of 
habits,  not  to  say  integrity  ;  but  I  will  acknowledge  it, 
the  rumour  has  not  reached  me. 

I  have  been  speaking  to  you  of  the  Man  ;  now  I  will 
treat  of  the  Minister. 

At  the  battle  of  Messenheim  (1800),  near  Inspruck, 
Championnet  I'cmarks  the  temerity,  the  intrepidity  of 
Colonel  Bisson,  and  demands  for  him,  with  the  applause 
of  all  the  army,  the  epaulettes  of  a  General  of  Brigade. 
Weeks  elapse,  and  the  commission  does  not  arrive.  Bis- 
son grows  impatient,  goes  to  Paris,  obtains  an  interview 
with  the  Minister,  and  in  his  anger,  apostrophizes  him  in 
a  rough  manner.  "  Young  man,"  Carnot  calmly  replied 
to  him,  "  it  is  possible  that  I  may  have  committed  an 
error;  but  your  improper  manners,  really,  might  disin- 
cline me  to  repair  it.  Go,  I  will  attentively  examine 
your  services."  "My  services!  Ah!  I  know  too  well 
that  you  despise  them,  you,  who  from  the  shelter  of  your 
cabinet  coolly  send  us  the  order  to  die.  Protected  from 
danger,  and  from  the  rigour  of  the  seasons,  you  have 
already  forgotten,  and  you  will  continue  to  forget,  that 

our   blood  flows,  and    that   we   lie  on    the  hard  ." 

"  Colonel,  this  is  too  much  !  For  your  own  interests, 
our  interview  must  not  continue  in  this  tone.  Retire  ! 
Your  address,  if  you  please  ?  Go!  you  will  shortly  hear 
from  me." 


114  CARNOT. 

These  last  words,  pronounced  in  a  solemn  tone,  un- 
sealed Colonel  Bisson's  eyes.  He  runs  to  a  devoted 
friend.  General  Bessieres,  to  seek  consolation.  His 
friend,  on  the  contrary,  gives  him  to  understand  that  a 
court-martial  will  be  the  inevitable  consequence  of  his 
folly.  In  the  mean  time  Bisson  hides  himself.  A  faith- 
ful servant  goes  every  hour  to  the  hotel,  to  learn  about 
the  dreaded  order  for  his  appearance.  The  ministerial 
paquet  at  last  arrives ;  Bisson,  all  emotion,  tears  open 
the  envelop.  The  paquet.  Gentlemen,  contains  the 
brevet  of  General  of  Brigade,  and  letters  of  service  ! 

It  is  scarcely  necessary  to  add,  that  the  new  general 
flies  to  Carnot  immediately  to  offer  him  the  homage  of 
his  admiration,  and  of  his  gratitude,  and  of  his  deep 
repentance.  All  this  proved  superfluous,  for  General 
Bisson  found  his  orders  at  the  door  of  the  Minister's 
office.  That  ardent  soul  which,  notwithstanding  all  its 
sincerity  of  conduct,  felt  the  act  somewhat  onerous, 
proved  how  well  he  had  appreciated  the  delicate  severity 
of  Carnot,  and  how  worthy  he  was  of  it,  by  that  very 
evening  publishing  the  details,  which  assuredly  Plutarch 
himself  would  not  have  disdained. 

Of  all  the  qualities  that  great  men  can  adorn  them- 
selves with,  diffidence  seems  the  least  obligatory ;  there- 
fore the  more  credit  is  given  to  them  for  it ;  and  there- 
fore also  it  leaves  the  most  durable  recollections.  Who, 
for  example,  does  not  know  by  heart  that  letter  which 
Turenne  wrote  to  his  wife,  a  hundred  and  seventy-nine 
years  ago,  on  the  day  -of  the  celebrated  battle  of  the 
Dunes: 

"  The  enemy  came  to  us  ;  they  have  been  beaten  ; 
God  be  praised.  I  have  worked  a  little  in  the  course 
of  the  day ;  I  wish  you  good  night,  and  will  go  to  lie 
down." 


CONCLUSION.  115 

Equally  with  this  illustrious  general  of  Louis  XIV. 
did  Carnot  omit  his  own  participation,  both  in  his  private 
communications  and  when  he  wrote  to  the  Convention. 
I  have  related  to  you  the  part  he  acted  at  the  battle  of 
Wattignies  ;  well,  read  the  bulletin  which  that  decisive 
and  memorable  event  inspired  him  to  write,  and  you  will 
in  vain  seek  a  few  words  to  recall  the  representative  of 
the  people ;  unless,  indeed,  we  are  determined  to  see 
them  in  this  passage  :  "  The  Republicans  charged  for- 
ward with  the  bayonet,  and  remained  victorious." 

But  all  of  you,  who  knew  Carnot,  will  agree  with  me, 
that  unless  he  was  pressingly  and  directly  solicited,  he 
would  never  entertain  you  with  the  European  events 
which  he  had  so  often  directed.  Justly  jealous  of  the 
esteem  of  France,  the  old  Director,  during  his  exile, 
answered  the  diatribes  of  his  accusers  in  writing.  His 
style  on  these  occasions  was  lively,  poignant,  and  cut 
deep ;  it  was  evident  at  each  line  that  it  proceeded  from 
an  ulcerated  heart.  Yet  the  most  legitimate  irritation 
never  led  him  beyond  the  circle  that  his  enemies  had 
traced  out.  His  defence  in  some  parts  might  resemble 
an  attack  ;  but  at  bottom,  on  close  examination,  it  was 
still  a  defence.  Carnot  rejected  far  from  him,  the  idea 
of  raising  a  pedestal  to  himself  with  the  immortal  trophies 
that  he  had  reaped  during  his  Conventional  and  Directo- 
rial career.  Modesty,  Gentlemen,  is  a  good  alloy  when 
it  triumphs  thus  over  anger. 

In  regard  to  science,  the  illustrious  academician  was 
not  less  reserved.  One  would  have  said,  indeed,  that  he 
regulated  his  conduct  according  to  that  reflection  of  the 
oldest  and  most  ingenious  of  your  interpi-eters  :  "  When 
a  learned  man  speaks  to  instruct  other  men,  and  exactly 
in  that  line  of  instruction  that  they  wish  to  acquire,  he 


116  CARNOT. 

does  them  a  favour ;  but  if  he   speaks  only  to  show  oiF 
his  own  learning,  they  do  him  a  favour  in  listening." 

Modesty,  moreover,  is  not  a  quality  deserving  of  re- 
spect and  esteem,  except  in  isolated  individuals.  Bodies 
of  men,  and  especially  academies,  would  be  guilty  of  a 
fault,  and  would  be  wanting  in  a  principal  duty,  if  they 
neglected  to  adorn  themselves  in  the  eyes  of  the  public 
with  the  legitimate  claims  they  have  earned  to  the 
esteem,  gratitude,  and  admiration  of  the  world.  The 
more  justly  celebrated  they  are,  the  stronger  is  the 
desire  to  belong  to  such  institutions,  and  the  more  the 
laborious  efforts  made  to  attain  this  aim  turn  to  the 
advantage  of  science,  and  to  the  glory  of  the  human 
mind.  This  thought  has  encouraged  me.  Gentlemen,  to 
unroll  to  your  eyes,  in  all  its  details  and  in  its  true  colours, 
the  very  eventful,  varied,  and  stormy  life  of  Carnot. 
For  nearly  two  centuries  the  Academy  of  Sciences  con- 
scientiously has  preserved  the  memory  of  the  geometers, 
the  physicists,  the  astronomers,  the  naturalists,  who 
have  rendered  it  illustrious.  The  name  of  the  great 
citizen  who  by  his  genius  preserved  France  from  foreign 
dominion,  has  appeared  to  me  to  deserve  being  inscribed 
with  some  solemnity  in  this  glorious  Pantheon. 


MALUS. 


A  BIOGRAPHY  PREPARED  FOR  THE  PUBLIC  SITTING  OF 
THE  ACADEMY  OF  SCIENCES,  1854;  AND  READ  BY 
SPECIAL  DESIRE  OF  THAT  LEARNED  BODY,  ON  THE 
8th    of    JANUARY,    1855. 


BIRTH     OP    MALUS. HIS     LITERARY     EDUCATION. — IIIS 

ADMISSION    TO    TPIE    POLYTECHNIC    SCHOOL. 

Stephen  Louis  Malus,  whose  name  will  be  per- 
petuated by  an  immortal  discovery  as  long  as  the  phys- 
ical sciences  shall  be  honoured  among  men,  was  born 
at  Pari:;,  on  the  23d  of  July,  1775,  his  parents  being 
Anne-Louis  Malus  of  Mitry,  treasurer  of  France,  and 
Louisa  Charlotte  Desbres. 

His  first  studies  were  principally  literary  ;  he  acquired 
a  very  sound  knowledge  of  the  authors  who  form  the 
glory  of  Greek  and  Latin  literature.  Up  to  his  latest 
years  he  continued  to  be  able  to  recite,  without  hesita- 
tion, long  passages  of  the  Iliad,  of  Anacreon,  Horace, 
and  Virgil.  Like  almost  all  scholars  gifted  with  some 
facility  of  composition,  he  rashly  devoted  his  youthful 
talents  to  productions  of  a  kind  really  above  his  powers, 
and  the  difficulty  of  which  one  of  our  great  poets  so 
energetically  characterizes  when  he  calls  them,  "oeuvres 
du  demon."      But  he  carried  out  his  endeavours  to  an 


118  MALUS. 

extent  beyond  what  is  usual.  I  liave  discovered  among 
the  papers  of  Malus,  tvA'o  cantos  of  an  epic  poem  entitled 
Themelie,  or  the  Foundation  of  France,  and  two  com- 
plete tragedies  ;  one  on  the  capture  of  Utica,  and  the 
death  of  Cato ;  the  other  recounting  the  dreadful  catas- 
trophes of  the  family  of  the  Atrides,  and  entitled  Electra. 
The  fact  that  some  beautiful  verses  and  some  interesting 
situations  occur,  Mould  not  hinder  me  from  avowing  that 
the  youthful  autlior  had  not  as  yet  discovered  his  true 
vocation,  were  it  not  tliat  the  immense  inequality  which 
we  observe  between  the  Hostile  Brothers  and  the  Andro- 
mache, though  both  worthy  of  Racine,  shows  with  what 
caution  we  ought  to  abstain  from  premature  judgment. 

Malus  pushed  forward  with  equal  and  distinguished 
success  the  study  of  letters,  and  of  algebra  and  geometry. 
He  went  through  the  examination  for  the  School  of  En- 
gineers at  Mezieres,  in  1793,  and  was  classed  the  same 
year  as  sub-lieutenant  in  the  promotion  in  which  General 
Bertrand  held  the  first  place.  But  the  serious  disorders 
of  which  the  school  of  Mezieres  was  the  theatre,  having 
caused  its  suppression,  Malus  could  not  profit  by  his  bre- 
vet of  admission.  He  enrolled  himself  as  a  volunteer  in 
the  15th  battalion  of  Pai'is,  and  proceeded  to  Dunkirk, 
where  he  took  part  in  the  manual  labour  of  the  wheel- 
barrow, as  a  common  workman  in  the  construction  of  the 
field  fortifications  with  which  that  place  was  being  sur- 
rounded. M.  Lepere,  engineer  of  roads  and  bridges,  who 
was  directing  a  part  of  these  constructions,  having  re- 
marked certain  peculiar  and  unexpected  arrangements  in 
the  manner  in  which  the  soldiers  executed  the  excava- 
tions and  raised  the  mounds,  was  desirous  to  learn  the 
origin  of  these  practices  ;  they  pointed  out  to  him  the 
man  who  had  indicated  these  as  the  means  best  suited  to 


EARLY    CAREER.  119 

attain  the  desired  end  with  the  least  possible  fatigue.  A 
few  moments'  conversation  showed  the  engineer  that  he 
had  found  in  the  humble  labourer  of  the  15th  Battalion 
of  Paris  a  superior  man  ;  and  he  accoi'dingly  sent  him  to 
the  "Ecole  Polytechnique,"  which  had  just  been  founded. 

Mains  then  was  one  of  the  first  pupils  of  this  celebrated 
institution.  He  soon  gained  the  good  will  of  Monge,  who 
became  his  friend ;  indeed  nothing  less  than  such  a  warm 
friendship  was  necessary  to  preserve  him  from  the  mis- 
fortunes he  would  have  incurred  from  his  taking  a  part 
in  the  many  political  movements  by  which  the  capital 
was  then  agitated. 

On  quitting  the  school,  Malus  went  to  Metz,  where  he 
was  received  as  a  pupil  sub-lieutenant  of  engineers  the 
20th  February,  1796.  He  was  named  captain  on  the 
19th  June  following;  and  was  sent  the  next  year  to  the 
army  of  the  Sambre  and  Meuse,  where  he  took  an  active 
and  distinguished  part  in  the  actions  in  which  that  valiant 
army  was  engaged. 

There  has  been  recently  found  among  the  family  pa- 
pers, a  small  bound  book,  in  which  Malus,  when  captain 
of  eno-ineers,  and  employed  in  the  army  of  th6  East, 
traced  day  by  day  an  abridged  narrative  of  all  the  events 
of  which  he  had  been  an  eyewitness,  or  in  which  he  had 
taken  a  direct  part.  These  memoranda,  which  I  have 
read  with  the  greatest  interest,  and  in  which  our  fellow 
labourer  figures  chiefly  as  a  military  man,  seem  to  me  to 
deserve  a  detailed  analysis.  I  have  resolved  to  layit 
before  you,  were  it  only  to  prove  once  more,  that  pro- 
found knowledge  and  a  scientific  genius  did  not  weaken 
either  the  zeal,  the  constancy,  the  courage,  or  the  spirit 
of  enterprise,  which  ought  to  distinguish  an  officer  of  the 
highest  military  qualities. 


120  MALUS. 

After  having  read  the  following  details,  few  would 
venture  to  estimate  their  own  services  above  those  which 
Malus,  the  man  of  science,  rendered  in  his  sphere. 

EGYPTIAN  CAMPAIGN. EXTRACTS  FROM  THE  MEMO- 
RANDA OF  MALUS. 

The  events  of  the  war  led  the  Captain  of  Engineers, 
Malus,  to  the  right  bank  of  the  Rhine.  He  remained 
eleven  months  in  garrison  in  the  learned  city  of  Giessen : 
he  was  even  on  the  point  of  contracting  a  marriage  with 
the  eldest  daughter  of  the  Chancellor  of  the  university, 
Professor  Koch,  when  the  order  came  for  him  to  proceed 
to  Toulon,  where  he  was  to  serve  under  Caffarelli  in  the 
left  wing  of  the  array,  collected  for  an  expedition  of  which 
scarcely  any  one  knew  the  destination. 

The  27th  of  Floreal,*  we  find  him  at  Toulon,  em- 
barked on  board  L'Aquilon,  a  vessel  of  seventy-four 
guns,  commanded  by  Thevenard,  and  making  part  of 
the  advance  guard  of  the  squadi-on.  The  22d  Prairial  t 
he  took  part  in  the  attack,  by  assault,  of  the  fortress  of 
Malta,  the  defenders  of  which,  he  says,  surrendered  after 
having  made  much  noise  and  done  little  mischief. 

After  a  short  sojourn  in  Malta,  INIalus,  at  the  desire  of 
General  Desaix,  commandant  of  the  division  which  had 
arrived  at  Civita  Vecchia,  went  on  board  the  Courageux, 
in  which  that  general  was  embarked.  He  remarks,  "  I 
had  in  all  respects  to  congratulate  myself  on  this  change." 
The  fleet  quitted  Malta  the  3d  of  Messidor,J  and  we  find 
Malus  on  the  13th  of  that  month  §  sailing  all  night  in  an 
undecked  sloop  in  search  of  the  General-in-Chief,  to  re- 
ceive his  orders  as  to  the  point  at  which  the  division  of 
Desaix  was  to  disembark. 

*  May  16.         f  10th  June,  1798.         f  June  21.        ^  July  1. 


EXTRACTS    FROM   HIS    MEMORANDA.  121 

On  the  17th*  Malus  was  attached  to  the  advanced 
guard  of  the  invading  army.  The  21st.t  in  the  evenino-, 
he  encamped  on  the  road  from  Ramanieli.  At  that  time 
the  corps  of  engineers  had  neither  ''material"  nor  troops. 
An  officer  of  this  service,  isolated  in  the  army,  was  often 
deprived  of  the  commonest  necessaries.  We  find  an  in- 
stance in  the  following  description,  which  I  quote  from 
the  memoranda  :  "  Wanting  a  picquet  to  which  to  attach 
my  horse,  I  tied  him  to  my  leg  ;  I  slept,  and  dreamt 
peaceably  of  the  pleasures  of  Europe."  On  the  25th,t 
he  took  part  in  the  glorious  battle  of  Chebreys  ao-ainst 
the  Mamelukes.  The  2d  Thermidor,§  at  the  battle  of 
the  Pyramids,  he  was  in  one  of  the  battalions  formed  in 
squares  on  the  right  wing  beside  General  Desaix. 

On  the  4th,||  in  the  morning.  Captain  Malus  went  with 
a  detachment  of  carbineers  into  the  island  of  Raouda 
reconnoitring  the  right  bank  of  the  Nile  to  Mekias  and 
sent  over  to  the  left  bank  the  boats  which  were  necessary 
to  enable  the  army  to  cross  the  river.  The  same  even- 
ing he  accompanied  General  Dupuis,  who  was  charo-ed 
with  regulating  the  conditions  of  the  ca])itulation  of  Cairo. 
On  the  loth  Thermidor,^  he  set  out  with  the  advanced 
guard  of  the  array,  which  marched  against  Ibrahim  Bey 
encamped  at  Belbeys,  and  took  a  very  active  part  in  the 
important  combats  which  signalized  this  expedition  ;  in 
which  many  military  errors  were  committed. 

Somewhat  later,  we  find  Malus  accompanyino'  General 
Regnier  in  a  reconnoitre  which  had  fur  its  object  the  de- 
termination of  the  exact  distance  from  Salchieh  to  the 
sea.  On  his  return  he  discovered  the  remarkable  ruin 
of  the  ancient  city  of  San,  or  Thamis.  It  was  durin«- 
this   expedition   that  he  learned  the  destruction  of  the 

*  July  5.     t  July  9.     J  July  13.     §  July  20.     1|  July  22.     ^  August  2. 

SEO.  SEE.  6 


122  MALUS. 

French  fleet  in  the  naval  battle  of  Aboukir  ;  and  we  read 
without  surprise  in  the  memoranda  that  he  reentered 
Cairo  fatigued,  ill,  and  a  prey  to  profound  gi-ief. 

About  the  period  of  which  we  are  si^eaking.  General 
Bonaparte  created  the  Institute  of  Egypt.  Malus  was 
one  of  its  first  members. 

Some  days  afterwards,  Malus  received  an  order  to  join 
General  Desaix  in  Upper  Egypt.  On  his  return  to 
Cairo  with  the  division  of  "  the  just  Sultan,"  he  was 
charged  with  the  duty  of  making  jireparations  for  the 
fete  of  the  4th  Vandemiaire,*  in  the  square  of  Esbekieh. 
"  This  was,"  he  says,  "  a  trifling  distraction  from  the  grief 
which  had  afilicted  me  for  some  time."  On  the  30th,t 
and  following  days,  Malus  powerfully  contributed  to  re- 
press the  insurrection  which  had  arisen  in  Cairo  ;  having 
arrested  with  his  own  hand,  in  the  heat  of  the  tumult, 
one  of  the  insurgents,  he  found  in  his  possession  objects 
which  he  knew  belonged  to  General  Caftarelli,  his  imme- 
diate commander  and  friend ;  from  these  he  believed  that 
he  had  been  killed  ;  and  it  was  not  till  after  two  days 
that  he  learned  that  CafiareUi  had  quitted  his  house  be- 
fore the  Turkish  revolters  had  pillaged  it. 

After  the  rebellion  had  been  suppressed.  Captain  Ma- 
lus commenced  the  establishment  of  a  fort  in  the  position 
whence  during  the  insurrection  they  had  cannonaded 
the  grand  mosque.  The  construction  of  this  fort  occu- 
pied him  a  long  time ;  it  received  the  name  of  Dupuis. 
Afterwards  he  commanded  at  the  reconnoitring  of  the 
communications  of  the  Nile  with  the  lake  Menzeleh  and 
with  Salchieh.  In  this  expedition  the  young  officer  made 
discoveries  of  great  interest  in  respect  to  archaeology,  and 
the  ancient  geography  o£  this  part  of  Egypt. 

*  September  25.  t  October  20. 


EGYPTIAN    CAMPAIGN.  123 

On  his  return  to  Cairo,  Captain  Malus  enjoyed  some 
little  leisure  ;  by  wliich  he  profited  in  order  to  examine 
in  detail  the  "  Well  of  Joseph,"  which  he  described  as  a 
masterpiece  of  perseverance  and  skill  in  construction. 
He  went  also  to  visit  the  colossal  pyramids  of  Gizeh,  in 
company  with  a  man  who  might  be  truly  called  the  colos- 
sus of  our  army  from  his  height  and  his  bravery,  General 
Kleber. 

When  the  army  set  out  on  the  expedition  to  Syria, 
Malus,  who  was  then  occupied  in  reconnoitring  the  Delta, 
was  attached  to  the  division  of  General  Klebei*.  We 
shall  not  follow  him  in  the  difficult  route  which  our  brave 
soldiers  had  to  traverse  almost  without  provisions  or 
drinkable  water ;  the  details  which  we  find  on  this  sub- 
ject in  the  memoranda  only  inspire  the  most  painful 
reflections ;  we  will  merely  say,  that  the  young  officer 
of  engineers  took  a  part  with  distinction  in  the  siege  of 
El-Harisch.  We  find  him  taking  by  assault,  and  with 
great  intrepidity,  an  advanced  post  situated  eighty  metres 
from  the  place, — commanding  in  the  trenches,  and  pusli- 
ing  the  sap  almost  up  to  the  foot  of  the  breach,  when  the 
enemy  offei'ed  to  capitulate.  Tlie  young  officer  denounced 
in  energetic  terms  the  breach  of  faith  of  which  our  gen- 
erals were  guilty  in  regard  to  the  prisoners,  in  forcing 
them  to  enlist  among  our  soldiers. 

Malus  relates  the  march  of  the  army  ^.dvancing  into 
Syria.  It  first  took  the  infection  of  the  plague  in  the 
town  of  Gaza,  abandoned  by  the  enemy ;  its  divisions 
arrived  at  length  before  Jaffa  and  invested  that  town,  of 
which  it  raised  the  siege.  The  operations  were  con- 
ducted in  a  way  which  was  not  conformable  to  the  rules 
of  the  science  originally  laid  down  by  Vauban.  Our 
young  officer  recounts  that  the  breaching  battery,  being 


124  MALUS. 

supported  by  armed  positions  on  too  small  a  scale,  was 
surprised  in  the  night  by  a  sortie  of  the  troops  from  the 
town.  The  heads  of  our  soldiers  carried  into  .Jaffa  were 
paid  for  by  their  weight  in  gold.  The  head  of  INIalus, 
however,  did  not  figure  in  the  number  of  these  bloody 
trophies,  for  the  sole  reason  that  at  the  moment  of  the 
silent  invasion  of  the  battery  by  the  Turks  he  was  asleep 
in  one  of  the  angles  of  the  entrenchments.  The  breach 
having  been  opened,  and  the  garrison  not  having  answered 
to  the  summons  made  them,  the  troops  advanced  to  the 
assault  to  the  sound  of  the  bands  of  all  the  regiments. 
Here  I  will  no  longer  abridge,  but  copy  : — 

"  The  enemy  was  overthrown,  discouraged,  and  retired, 
after  a  sharp  firing  of  musquetry  from  the  houses  and 
forts  of  the  city  ;  they  kept  their  ground,  however,  at 
some  points,  and  continued  their  fire  for  an  hour.  Dur- 
ino-  this  time  the  soldiers,  scattered  through  all  parts, 
killed  men,  women,  children,  old  persons.  Christians,  and 
Turks  ; — every  thing  that  bore  the  human  form  was  the 
victim  of  their  fury. 

"  The  tumult  of  carnage,  the  broken  doors,  the  houses 
shaken  by  the  noise  of  the  firing  and  of  arras,  the 
cries  of  the  women,  the  father  and  child  overthrown  one 
on  the  other,  the  violated  daughter  on  the  corpse  of  her 
mother  ;  the  smoke  of  dead  bodies  burned  in  their  gar- 
ments which  had  been  set  on  fire,  the  smell  of  blood,  the 
groans  of  the  wounded,  the  cries  of  the  conquerors  dis- 
puting together  over  the  spoils  of  their  expiring  prey, 
infuriated  soldiers  responding  to  the  cries  of  despair  by 
exclamations  of  rage  and  redoubled  blows ;  lastly,  men 
satiated  with  blood  and  gold,  falling  down  in  mere  weari- 
ness on  the  heaps  of  corpses ; — such  was  the  spectacle 
which  this  unfortunate  city  presented  until  night." 


SIEGE    OF    JAFFA. 


125 


This  forcible  passage  of  the  manuscript  of  Mains  is 
the  faithful  picture  of  what  happens  in  every  town  taken 
by  storm,  even  when  the  assailants  belong  to  the  most 
humane  civilized  army  in  the  world.  AVhen  historians 
know  how  to  place  themselves  in  a  more  elevated  sphere, 
to  free  themselves  from  routine,  and  to  follow  in  the 
opinions  they  express  the  eternal  rules  of  justice  and 
humanity,  while  they  praise  the  indomitable  courage  of 
soldiers  who  will  brave  death  in  obedience  to  discipline, 
they  will  accord  a  deeper  sympathy  to  the  men  who  to 
preserve  their  nationality  consent  to  expose  themselves 
to  scenes  of  massacre  and  bloodshed  such  as  those  which 
the  narrative  of  Malus  has  revealed  in  all  their  horrors  ; 
their  condemnation  will  be  reserved  for  those  who  pro- 
voke these  impious  wars,  which  have  no  other  motive 
than  personal  ambition,  and  the  desire  for  a  vain  and 
false  glory. 

When  the  army  set  out  for  the  attack  on  the  town  of 
St.  John  d'Acre,  Malus  received  an  order  to  remain  at 
Jaffa  with  General  Grezieux.  There  were  left  with 
him  only  150  efficient  men  ;  the  town  contained  more 
than  300  wounded  and  400  infected  with  the  plague. 
Malus  was  charged  with  the  arrangements  necessary  to 
be  made  in  the  Greek  Convent,  in  order  to  establish 
there  those  suffering  with  the  plague.  For  ten  days 
successively  he  passed  all  liis  mornings  in  the  infected 
air  of  this  receptacle  of  corruption.  Thus  our  celebrated 
painter  Gros  might  have  legitimately  placed  the  portrait 
of  Malus  among  the  figures  in  tliat  admirable  picture  for 
which  modern  art  is  indebted  to  him,  in  the  place  of 
some  of  those  conventionally  introduced  there,  who  never 
really  penetrated  into  the  halls  then  choked  up  with  the 
dying  and  dead. 


126  MAI.US. 

The  eleventh  day,  Mains  felt  himself  infected  with  the 
terrible  disease  wliich  decimated  our  army.  From  this 
moment  I  will  allow  him  to  speak  for  himself;  science 
may  perhaps  derive  some  advantage  from  the  details 
which  I  transcribe  : — 

"  A  burning  fever,  and  violent  pains  in  the  head, 
forced  me  to  seek  repose ;  a  continued  dysentery  was 
added  ;  and  one  by  one  the  symptoms  of  plague  showed 
themselves.  About  the  same  time  General  Grezieux 
died.  Half  of  the  garrison  had  already  been  struck ; 
thirty  soldiers  fell  victims  daily ;  Brinquier,  who  had 
taken  my  place  in  superintending  the  hospital,  was  seized 
on  the  fourth  day,  and  died  forty-eight  hours  afterwards. 
At  this  period  characteristic  bubo  showed  itself  on  my 
right  groin.  I  had  all  along  up  to  this  time  entertained 
hope  that  my  disease  might  not  be  the  plague ;  the  num- 
ber of  days  I  had  lived  since  the  first  attack  seemed  to 
indicate  it ;  but  since  the  bubo  appeared,  and  the  pains 
at  the  heart  were  redoubled,  I  could  no  longer  feel  any 
doubt ; .  I  resigned  myself  to  my  fate.  I  sent  to  Fran- 
cisqui,  who  was  with  the  wounded  General  Damas,  the 
articles  which  I  wished  to  leave  to  my  relations  and 
friends.  I  ought  to  remark  that  Francisqui  was  the  sole 
one  of  my  comrades  who  had  not  abandoned  me,  and 
who,  in  order  to  tranquillize  me,  had  not  hesitated  to 
come  near  me  ;  on  the  day  of  his  departure  he  carried 
his  devotion  to  such  an  extent  as  to  embrace  me,  though 
he  was  then  certain  that  I  was  infected. 

"  Only  one  man  in  twelve  escaped.  St.  Simon  arrived 
in  Egypt  and  came  to  see  me  ;  he  was  then  in  perfect 
health,  in  two  days  afterwards  he  was  dead.  The  siege 
of  Acre  was  protracted,  the  sick  fell  back  on  Jaffa  and 
increased   the  numbers  of  the  dying ;  besides  this,  the 


IN    QUARANTINE.  127 

plague  was  in  every  house  of  the  town  where  there  still 
were  any  inhabitants.  The  refugees  of  Ramie,  who 
came  to  Jaffa  to  place  themselves  under  our  protection, 
perished  nearly  to  a  man.  The  Convent  of  the  Capu- 
chins, which  was  placed  in  quarantine,  could  not  escape 
the  contagion  :  the  greater  part  of  the  monks  died.  All 
the  Frank  families  perished  except  two  men  and  one 
woman. 

"  I  no  longer  knew  a  single  individual  among  those 
now  at  Jaffa.  I  had  lost  successively  my  friends,  my 
acquaintance,  and  my  servants  ;  there  only  remained  my 
French  servant,  who  attended  me  with  constancy  during 
my  illness,  and  he  died  at  my  side  the  24th  Germinal.* 
I  was  now  alone,  without  strength,  without  help,  without 
friends ;  I  was  so  exhausted  by  the  dysentery  and  the 
continual  suppurations,  that  my  head  became  extraordi- 
narily weakened  ;  the  fever,  which  redoubled  its  inten- 
sity at  night,  often  made  me  delirious  and  agitated  me 
terribly.  Two  men  of  the  corps  of  sappers  undertook 
the  care  of  me,  and  they  perished  one  after  the  other. 

"  At  length  on  the  2d  Floreal  f  I  was  put  on  board 
L'Etoile,  which  was  setting  sail  for  Egypt  and  whose 
captain  had  the  plague  ;  he  died  the  night  of  our  arrival 
at  Damietta.  •  The  sea  air  produced  a  sudden  effect  on 
me  ;  it  seemed  to  me  as  if  I  were  relieved  from  suffo- 
cation. After  the  first  day  I  almost  began  to  feel  some 
wish  for  food,  I  was  nevertheless  very  feeble.  Contrary 
winds  kept  us  several  days  out  at  sea  ;  this  delay  pro- 
duced a  very  marked  amendment  in  my  health  ;  my 
strength  revived,  the  crust  of  the  bubo  fell  off;  my  appe- 
tite was  restored. 

"  On  the  7th  Floreal  I  we  came  to  anchor  before  the 

*  April  12,  1799.  f  April  21.  J  April  26. 


128  MALUS. 

Bogaz  of  Damietta ;  on  the   8th  *  we  entered  the  Nile 
and  the  vessel  was  put  under  quarantine." 

If  any  one  would  wish  to  know  how  our  institutions, 
"when  entrusted  to  persons  destitute-  of  humanity,  add 
fresh  sufferings  to  those  of  natural  afflictions,  let  him  con- 
tinue with  us  the  transcription  of  jNIalus's  harrowing 
recital. 

"The  10th  Germinal t  I  disembarked  and  was  con- 
ducted to  the  lazaretto  of  Lesbieh,  where  were  collected 
those  suffering  from  the  plague  from  Damietta  as  well  as 
those  arrived  from  Syria.  They  placed  also  with  me 
several  passengers  who  had  no  symptom  of  the  disease, 
but  who  in  due  course  took  the  infection  in  the  lazaretto 
and  died,  every  one  of  them.  These  numerous  deaths 
delayed  the  period  of  my  enlargement.  It  was  rare  that 
any  one  got  out  of  this  infernal  prison  who  had  once  had 
the  misfortune  to  enter  it ;  hardly  would  they  condescend 
to  succour  the  unhappy  persons  who  came  to  spend  their 
last  hours  there.  I  have  often  seen  them  die  with  rage 
demanding  water  of  the  barbarians  who  pretended  that 
they  did  not  understand  them'  or  would  answer,  '  It  is 
not  worth  while.'  Greedy  grave-diggers  robbed  the  dy- 
ing persons  before  they  had  yielded  their  last  breath  ; 
these  unworthy  agents  of  the  sanitary  commission  were 
the  only  inedical  attendants,  the  only  guardians  allowed 
to  the  sick.  Hardly  had  their  victims  ceased  to  live 
when  they  carried  them  over  to  the  opposite  shore, 
where  they  abandoned  them  to  the  dogs  and  birds  of 
prey.  Sometimes  they  covered  them  with  a  little  sand  ; 
but  the  wind  soon  exposed  the  bodies  naked,  and  the 
cemetery  presented  the  hideous  spectacle  of  a  field  of 

*  April  27. 

t  Probably  a  mistake  for  Floreal,  April  30. 


LIBERATED    FROM    THE    LAZARETTO.  129 

battle.  One  wretched  woman,  of  whom  I  had  taken 
care  because  she  was  absolutely  deserted,  begged  of  me 
the  evening  of  her  death  to  give  a  piastre  to  the  grave- 
diggers,  that  she  might  be  preserved  from  becoming  a 
prey  to  the  jackals.  I  fulfilled  her  wish,  and  caused 
them  to  bury  her  at  the  extremity  of  the  plain  where  the 
dead  were  deposited. 

"  I  had  been  already  a  month  in  this  abominable 
abode,  when  Cazola  obtained  for  me  the  privilege  of 
being  put  in  quarantine  in  a  separate  lodging.  My  soli- 
tude appeared  to  me  delicious,  because  I  had  quitted  the 
society  of  the  dying.  I  succeeded  in  reestablishing  my 
health,  and  in  the  beginning  of  Messidor,*  I  received 
definitively  my  liberty,  which  followed  the  sacrifice  of  all 
my  property." 

How  heartily  must  we  not  congratulate  ourselves  that 
Mains  escaped,  in  so  unhoped-for  a  way,  from  the  terri- 
ble stroke  which  had  mowed  down  so  many  victims  !  If 
he  had  fallen  under  it,  the  beautiful  branch  of  optical 
science,  of  which  he  planted  the  first  signal  after  his 
return  to  France,  perhaps  would  not  have  been  created, 
and  the  admirable  progress  which  the  science  has  made 
would  not  have  been  reckoned  among  the  most  striking 
claims  to  the  admiration  of  posterity  of  which  the  19th 
century  may  boast.  Some  time  after  this,  Malus  was 
ordered  to  proceed  to  Cathieh,  where  he  established  him- 
self. The  delights  of  this  advanced  post,  where  General 
Le  Clerc  commanded,  are  described  con  amove  by  him 
who  had  just  escaped  the  frightful  disease,  and  the  dan- . 
gers  not  less  dreadful  of  the  lazaretto  of  Lesbieh. 

"  We  encamped,"  he  says,  "  in  huts  whose  walls  and 
roofs   were   composed  of    palm-leaves    interwoven ;    we 

*  June  19=Messi(lor  1. 

6* 


130  MALU3. 

were  lodged  like  Arabs  ;  I  had  close  to  my  cabin  a  small 
enclosure  containing  my  horses,  camels,  and  asses  ;  an 
aviary  full  of  fowls,  geese,  and  ducks,  a  pen  for  my  two 
sheep,  another  for  a  boar ;  houses  for  my  pigeons,  and 
my  goat  enjoyed  its  liberty.  It  was  in  a  great  measure 
in  this  society  that  I  passed  three  months  of  my  sojourn 
in  Egypt  which  were  to  me  particularly  agreeable.  A 
perfect  tranquillity,  peaceable  enjoyments,  and  waiting 
for  an  enemy  whom  we  calculated  on  conquering,  hin- 
dered us  from  wishing  for  conveniences  of  which  we  . 
were  deprived." 

Malus  here  does  not  say  all  ;  at  Cathieh  he  composed 
a  memoir  on  light,  of  Avhich  we  shall  have  occasion  to 
speak  presently.  If  it  should  happen  that  in  analyzing 
this  work,  we  should  find  therein  some  results  which 
may,  or  which  ought  to  be,  contested,  we  may  remark 
that  it  was  composed  half  a  century  ago,  and  that  the 
author  was  in  a  position  truly  exceptional  when  he  was 
engaged  in  it. 

I  find  mentioned  in  the  memoranda  that  in  a  re- 
connoissance  which  he  made  with  a  detachment  of 
dromedaries  of  which  he  had  the  command,  Malus 
encountered  a  caravan,  attacked  it,  dispersed  it,  and 
obtained  a  great  number  of  camels,  and  a  quantity  of 
provisions. 

On  quitting  Cathieh,'-  Malus  went  to  Cairo,  where  he 
received  from  Kleber  (October  21,  1799,)  the  brevet 
rank  of  Chief  of  Battalion,  the  just  recompense  of  such 
active  services  and  so  much  courage  displayed  by  the 
young  captain,  ever  since  the  first  disembarkation  of  the 
French  army  in  Egypt.  The  commandant  Malus  having 
learnt  at  Cairo  that  a  disembarkation  of  Turks  was  pre- 
paring near  Damietta,  hastened  thither ;    where,  when 


PROMOTION    AND    SERVICES.  131 

he  arrived  the  8th  Brumaire,*  he  found  the  enemy 
ah-eady  fortified.  The  next  day  but  one,  after  having 
been  in  the  trenches  during  the  morning,  he  joined,  as  a 
private  foot  soldier,  the  troops  who  charged  the  Osman- 
lis  with  the  bayonet,  and  precipitated  them  into  the  sea. 

On  the  20th  Friraaire,t  Malus  received  the  command 
of  the  position  at  Lesbieh,  where  he  had  destroyed  the 
Avails  wlien  this  fortress  was  in  the  hands  of  the  Turks, 
and  which  he  had  rebuilt  since  it  had  fallen  into  the 
power  of  the  French.  On  the  22d,  |  the  plague  made 
its  appearance  at  Lesbieh  in  six  different  quarters ;  the 
commandant,  Malus,  from  his  long  experience,  applied 
means  of  preventing  its  development  and  propagation  ; 
nevertheless  it  made  many  victims  till  the  28th  Plu- 
viose.§  On  the  29th. ||  the  position  of  Lesbieh  was  sur- 
rendered to  the  Osmanlis  in  virtue  of  the  convention  of 
El  Harisch.  Malus  arrived  at  Cairo  the  25th  Ventose,*I[ 
and  on  the  28th  **  learned  the  rupture  of  the  capitula- 
tion of  El  Harisch  by  Lord  Keith.  The  same  day,  at 
two  o'clock  in  the  afternoon,  appeared  the  proclamation 
of  Kleber,  which  ended  with  these  celebrated  and  pro- 
phetic words  :  "  The  army  will  respond  to  this  disloyal 
proceeding,  and  to  the  demand  to  lay  down  their  arms, 
by  new  victories."  The  army  was  in  fact  on  its  march 
on  the  next  day  to  fight  the  forces  of  the  Grand  Vizier. 
Malus,  attached  to  tlie  division  of  General  Friant,  per- 
sonally took  part  in  the  immortal  battle  of  Heliopolis, 
when  11,000  men  triumphed  over  more  than  60,000. 

The  day  after  the  victory  a  particular  circumstance 
which  I  find  related  in  the  memoranda,  had  some  unfor- 
tunate consequences.     "  On  the  30th,tt  at  two  o'clock  in 

*  October  29.  §  February  26,  1800.  **  March  18. 

t  December  10.  ||  February  27.  tt  Miiroh  20. 

J   December  12.  ^  March  lo. 


132 


MALUS. 


the  morning,"  Mains  says,  "the  army  commenced  its 
march  for  Belbeys,  where  we  reckoned  on  finding  the 
Turkish  army  collected.  I  went  with  the  division  of 
Friant.  After  an  hour's  march  I  suspected  that  we 
were  losing  our  way  in  the  desert.  As  the  night  was 
very  dark  we  had  lost  the  ordinary  tracks.  I  repre- 
sented the  matter  to  the  general,  who  listened  to  me  for 
a  moment,  but  other  persons  brought  forward  opposite 
opinions  with  so  much  assurance,  that  the  march  was 
continued.  One  hour  and  a  half  afterwards,  we  were 
taking  a  direction  exactly  towards  the  point  whence  we 
had  started.  This  1  perceived  from  the  position  of  the 
pole  star,  which  we  had  at  starting  behind  us.  This 
time  I  was  listened  to,  and  I  led  back  the  division  on  the 
right  route.  This  mistake  nevertheless  caused  us  much 
delay,  and  the  other  divisions  were  obliged  to  wait  for 
us  at  one  league  distance  from  Belbeys." 

We  see  on  what  little  circumstances  the  great  events 
of  war  often  depend.  If  there  had  been  in  the  division 
of  Friant  only  an  ordinary  small  compass  of  a  few  milli- 
metres in  diameter,  like  those  which  are  hung  among 
the  trinkets  to  watches,  or  even  if  self-conceited  officers 
had  not  obtained  a  preference  for  their  opinions  over 
that  of  Mains,  the  divisions  of  our  army  would  have 
been  reunited  much  sooner ;  and  that  of  the  Grand 
Vizier  would  have  experienced  near  Belbeys  very  con- 
siderable losses. 

Mains,  now  attached  to  the  division  of  General  Reg- 
nier,  took  part  in  the  expedition  which,  after  several 
serious  affairs,  drove  back  the  Ottoman  army  across  the 
desert.  Afterwards  he  returned  to  Cairo,  then  in  a 
state  of  revolt  excited  by  the  Mamelukes,  who,  on  the 
day  of  the   battle  of  Heliopolis,  fell  back  on  the   great 


HIS    MARRIAGE.  133 

city.  We  see  at  once  the  nature  of  the  service  of  an 
officer  of  engineers  in  such  an  attack  as  that  on  Cairo, 
■where  he  was  obliged,  in  order  to  take  the  barricades, 
to  turn  them  by  passing  through  the  interior  of  the 
houses.  After  the  complete  surrender  of  Cairo,  Malus 
was  quartered  at  Gizeh,  when  on  the  25th  Prairial,* 
General  Kleber  was  assassinated  in  his  garden  at  Cairo 
by  a  Tui-k  arrived  from  Syria. 

We  will  here  terminate  the  long  extract  from  the 
memoranda  of  Malus.  It  would  be  too  painful  to  us  to 
follow  the  well-founded,  but  very  bitter  criticisms  which 
he  directs  against  General  Menou.  A  single  trait  will 
suffice  to  show  his  opinion  of  the  former  Commander- 
in-Chief  of  the  army  of  the  East.  "  Kleber,"  says 
Malus,  "  was  assassinated  on  the  24th  Pi-airial ;  some 
days  afterwards  General  Menou,  in  attacking  the  hon- 
our of  the  deceased  General  Kleber,  has  assassinated 
him  over  again." 

In  going  over  the  memoranda,  which,  amid  the  chan- 
ces of  war,  might  very  probably  fall  into  the  hands  of 
indiscreet  persons,  friends  or  enemies,  I  remarked  that 
Malus  indicates  very  exactly  the  date  at  which  he 
received  letters  from  his  father,  his  uncle,  &c.  As  to 
letters  from  Giessen  (and  we  easily  guess  whose  hand 
wrote  them)  he  gives  no  indication  or  trace.  I  notice 
this  extreme  delicacy  for  the  instruction  of  ill-informed, 
or  malevolent  persons,  who  believe  sentiments  of  the 
kind  referred  to  incompatible  with  geometrical  studies. 

MARRIAGE    OF    MALUS. — HIS    MILITARY    CAREER. 

Malus  quitted  Egypt  and  made  the  voyage  on  board 
The  Castor,  an  English  transport  ship,  according  to  tlie 
*  .Tune  13. 


134  MALtJS. 

arrangement  made  between  General  ISIenou,  Comman- 
der-in-Chief of  our  army,  and  the  hostile  generals.  He 
arrived  at  Marseilles  the  1st  October,  1801,  and  was 
immediately  put  into  quarantine.  After  the  pestiferous 
scenes  of  Jaffii,  of  Damietta,  and  Lesbieh,  he  must  have 
found  the  lazaretto  in  which  he  was  now  confined  a 
place  of  luxury.  As  soon  as  he  w^as  set  at  liberty  he 
repaired  to  Paris.  After  a  short  visit  to  his  relations, 
bound  by  his  sentiments  even  more  than  by  his  promise, 
he  hastened  to  Giessen,  where  he  once  more  joined 
Mademoiselle  Wilhelraine  Louise  Koch,  affianced  tp  him 
for  four  years,  and  was  married  to  her.  This  union 
completed  his  happiness  ;  we  shall  soon  have  to  relate 
the  rare  proof  of  devotion  which  Madame  Malus  gave 
the  husband  of  her  choice  during  the  afflicting  illness 
which  took  him  from  her  and  from  the  sciences. 

The  subsequent  military  career  of  Malus  may  be 
stated  in  a  few  lines.  In  1802-3  he  was  employed  at 
Lille.  We  find  him  in  1804  at  Antwerp,  planning 
measures,  according  to  the  orders  of  Napoleon,  for 
completing  the  naval  establishment  of  the  city,  and  ex- 
tending its  lines  of  fortification.  In  this  elaborate  work, 
the  account  of  which  is  preserved  in  the  depot  of  fortifi- 
cations, accompanied  by  eleven  sheets  of  drawings,  the 
author  treats  analytically,  but  without  neglecting  the 
arithmetical  applications,  two  questions  of  mechanics, 
which,  under  the  circumstances  and  in  that  locality,  pos- 
sess a  great  importance,  viz :  1.  The  amount  which, 
ought  to  be  deducted  for  the  weight  of  men  marching  in 
a  tread-wheel,  to  move  the  inclined  twisted  pipes,  or 
Archimedean  hydraulic  screws,  used  in  draining :  2.  The 
employment,  for  the  same  purpose,  of  the  force  of  wind, 
acting  on  wind-mills  luiving  horizontal  sails  disposed  in 


MEMOIR    ON    LIGHT.  135 

such  a  way  as  to  turn  always  in  the  same  direction.  In 
1805,  Malus  was  attached  to  the  Army  of  the  North. 
In  1806-7-8,  he  was  sub-director  of  the  fortifications 
of  Strasbourg.  In  this  capacity  he  presided  over  the 
reconstruction  of  the  fortifications  of  Kehl,  and  made 
some  very  judicious  remarks  on  the  form  of  the  revet- 
ments,* and  applied  an  exact  analysis  to  the  determina- 
tion of  their  thickness.  In  1809  he  was  recalled  to 
Paris.  He  became  major  of  engineers  in  1810.  The 
archives  of  the  Committee  of  Arms  prove  that  the  in- 
spectors-general often  consulted  him  with  much  advan- 
tage on  the  merit  of  works  submitted  to  them. 

MEMOIR    ON    LIGHT. COMPOSED    IN    EGYPT. 

We  have  henceforth  to  occupy  ourselves  only  with 
the  life  of  Malus  as  a  physicist  and  member  of  the 
Academy  ;  without  departure  from  this  view,  I  may  say 
a  few  words  on  the  optical  memoir  which  he  composed 
in  the  hut  at  Lesbieh. 

The  author  announces  clearly,  in  the  first  part  of  the 
MS.  memoir  which  I  have  before  me,  the  object  which 
he  proposes  ;  this  is  to  prove  that  light  is  not  a  simple 
substance  ;  that  its  constituent  principles  are  caloric  and 
oxygen,  in  a  particular  state  of  combination.  To  estab- 
lish this  theory,  he  cites  numerous  facts  furnished  by 
chemistry,  which  prove  that  he  was  perfectly  initiated, 
not  only  in  the  general  principles,  but  even  in  the 
details  of  this  science.  It  must  be  observed,  however, 
that  all  the  deductions  of  Malus,  even  the  most  plausible 
at  the  present  day,  can  be  subverted  by  a  single  word  ; 
it  sutfices  to  cite,  in  contradiction  to  all  the  phenomena 

*  The  masonry  encasing  and  supporting  the  earthworks  in  a  for- 
tification. 


136  MALUS. 

which  our  friend  alleges,  the  instance  of  the  light  which 
is  engendered  in  a  vacuum,  by  the  aid  of  the  voltaic 
current,  passed  through  simple  substances,  such  as  car- 
bon, platinum,  &c. 

In  the  second  part  of  the  memoir  Malus  seeks  to 
establish  that  the  different  natures  of  various  lights  only 
differ  from  each  other  in  the  greater  or  less  proportion 
of  caloric  which  they  contain.  The  red  light  would 
thus  be  the  most  heating,  the  violet  the  least  so,  which 
agrees  with  experiment.  According  to  a  singular  opinion 
professed  by  the  author,  all  rays,  if  possessing  a  certain 
high  intensity,  ought  to  produce  the  sensation  of  white- 
ness,* 

The  third  part  of  the  work  is  devoted  to  mechanical 
consequences  which  result  by  analysis  from  the  supposi- 
tions explained  in  the  first  two  sections.  It  may  suffice 
to  say,  that  the  author  finds,  like  all  the  partisans  of  the 
system  of  emission,  that  the  velocity  of  light  ought  to  be 
greater  in  water  than  in  air :  every  one  therefore  will  see 
how  superfluous  it  would  be  now  to  go  into  a  discussion 
of  the  details  of  such  a  subject. 

*  The  "singular"  opinion  here  ascribed  to  Mains  is  perhaps  not 
altogether  without  foundation,  at  least  in  some  cases.  It  is  certain 
that  while  the  prismatic  spectrum  of  the  white  light  of  the  clouds 
present  a  clear  yellow  and  green  portion,  that  same  portion,  when  the 
direct  rays  of  the  sun  are  substituted,  appears  to  the  eye  intensely 
brilliant  and  white.  And  it  is  far  from  certain  that  in  some  other  ex- 
periments, which  have  been  the  occasion  of  some  little  controversy 
and  where  the  colour  of  certain  parts  of  the  spectrum  has  appeared 
to  undergo  a  change,  the  intensity  of  the  light  reaching  the  eye  may 
not  be  concerned.  In  fact,  the  sensation  of  colour  is  one  so  entirely  de- 
pendent on  unknown  physiological  causes,  that  we  can  hardly  venture 
to  predict  what  the  result  may  be  on  different  individual  eyes,  though 
all  the  optical  conditions  may  be  precisely  the  same.  It  may  not  be 
altogether  without  a  bearing  on  this  subject,  to  remark  the  extremely 
contradictory  statements  made  by  different  observers  as  to  the  colour 
of  intenselv  brilliant  meteors. —  Trunslntor. 


MEMOIR    ON    LIGHT.  137 

The  memoir  of  which  I  am  speaking  was  destined  for 
the  Institute  of  Egypt.  I  find  in  fact,  in  a  letter  from 
Malus  to  Lancret,  the  following  passage  : — 

"  I  send  you,  my  dear  Lancret,  the  work  of  which  I 
have  already  spoken  :  mark  out  for  me  those  things  in  it 
which  any  one  might  call  repetitions  of  what  has  been 
already  said,  or  which  are  useless  ;  if,  after  this  expurga- 
tion, it  sliould  be  reduced  to  zero,  we  will  put  it  aside, 
and  there  will  be  no  more  question  about  it." 

It  is  just  to  remark,  after  the  critique  from  which  I 
could  not  abstain  when  I  considered  that  my  task  was 
not  that  of  a  panegyrist  but  of  a  biographer  aiming  at  the 
truth,  that  the  third  part  of  the  memoir  was  written  be- 
fore the  publication  of  the  fourth  volume  of  the  Mecan- 
ique  Celeste,  in  which  the  same  subject  is  treated  with 
the  greatest  care.  I  would  add  that  no  army  in  the 
world  ever  before  counted  in  its  ranks  an  officer  who 
occupied  himself  in  the  spare  hours  of  advanced_  posts 
with  researches  so  complete  and  so  profound.  The  truth 
of  this  remark  is  not  affiscted  by  the  recollection  which  it 
brings  up  of  the  expedition  of  Alexander.  It  is  true, 
men  of  science,  at  the  recommendation  of  Aristotle,  then 
accompanied  the  great  general  :  but  their  mission  was 
solely  to  collect  the  scientific  achievements  of  the  con- 
quered nations,  and  not  to  make  advances  in  the  sciences 
by  their  own  labours.  This  difference,  altogether  in 
favour  of  the  French  army,  deserves,  I  think,  to  be  here 
noticed.* 

I  see  by  a  letter  of  Lancret,  of  the  14th  Vendemiaire,t 

*  If  this  comparison  were  worth  carrying  out.  the  author  might 
have  added  that  the  men  of  science  in  Alexander's  expedition  were 
not  officers  of  (he  army  charged  at  the  same  time  with  onerous  and 
hazardous  duties,  but  leisurely  investigators,  having  no  other  occupa- 
tion.—  Translator. 

t  October  5,  1800. 


138  MALUS. 

an.  IX.,  that  Malus  was  occupied  theoi*eticallj  with  that 
most  important  meteorological  question,  the  distribution 
of  heat  in  different  climates.  I  have  never  been  able  to 
find  what  has  become  of  this  work. 

TREATISE    ON    ANALYTICAL    OPTICS. 

On  the  20th  April,  1807,  Malus  presented  to  the  first 
class  of  the  Institute,  a  treatise  on  analytical  optics,  in 
which  he  treats  of  rays  of  light  by  geometry  of  three 
dimensions. 

The  choice  of  academicians  to  whose  examination  the 
work  was  entrusted,  sufficiently  indicates  the  reputation 
which  the  author  had  already  acquired.  These  commis- 
sioners were  Lagrange,  Laplace,  Monge,  and  Lacroix. 
The  report  of  this  distinguished  commission  was  pre- 
sented by  Lacroix,  and  bears  date  the  19  th  October, 
1807.      ■ 

The  author  of  the  memoir  examines  the  nature  and 
relative  position  of  the  surfaces  formed  by  straight  lines 
successively  intersecting  one  another  according  to  given 
laws.  After  having  deduced  from  his  researches  some 
general  theorems,  of  a  very  remarkable  kind,  he  pro- 
ceeds to  make  an  application  of  them  to  the  case  of  rays 
of  light  proceeding  in  similar  directions,  either  by  reflex- 
ion or  by  refraction.  He  thus  generalizes  the  theory 
of  plane  caustics,  formerly  broached  by  Tschirnhausen. 
Among  the  curious  results  which  he  deduces  from  his 
formulas,  we  Avill  merely  quote  the  following  : — 

"  Reflexion  and  refraction  furnish  sometimes  optical 
images  which  are  erect  in  one  of  their  dimensions  and 
inverted  in  the  other." 

The  report,  for  which  I  will  not  presume  to  substitute 
my  personal  opinion,  concludes  in  these  terms  : — 


REFRACTIVE    POWER.  139 

"To  apply  thus,  without  any  limitation  on  its  general- 
ity, calculation  to  phenomena  ; — to  deduce,  from  a  single 
consideration  of  a  very  general  kind,  all  the  solutions 
■which  before  were  only  obtained  from  particular  consid- 
erations,— is  truly  to  write  a  treatise  on  analytical  optics, 
which,  concentrating  the  whole  science  in  a  single  point 
of  view,  cannot  but  contribute  to  the  extension  of  its  do- 
main." 

The  Academy  decided  (which  is  the  highest  degree  of 
approbation  it  can  bestow)  that  the  memoir  of  Malus 
should  be  printed  in  the  liecueil  des  Savants  Etrangers* 

MEMOIR     ON     THE     REFRACTIVE     POWER     OP     OPAQUE 
BODIES. 

On  the  16th  November,  1807,  Malus  presented  to  the 
Academy  a  memoir  in  which  he  treats  a  point  of  optics 
of  great  importance,  a  question,  in  fact,  involving  no  less 

*  Malus's  analytical  theory  contained  in  bis  Traite  c?  Opiique,  is  pre- 
fixed to  his  prize  memoir  on  Double  Refraction,  Paris,  1810. 

The  ordinary  deviations  by  reflexion  or  refraction  which  rays  un- 
dergo on  impinging  on  given  surfaces,  may  be  investigated  in  all  the 
simpler  cases  by  means  of  elementary  geometrical  constructions,  lead- 
ing to  the  theory  of  foci,  caustics,  &c.  But  more  general  investiga- 
tions of  the  same  kind  have  been  pursued  by  considering  the  algebraic 
equations  of  rays  undergoing  such  deviations.  This  higher  generaliza- 
tion leads  to,  and  includes,  the  same  results.  An  excellent  discussion 
of  the  subject  treated  in  this  point  of  view  will  be  found  in  Dr.  Lloyd's 
Treatise  on  Light  and  Vision.  It  is  a  still  higher  generalization  of  this 
kind  which  was  followed  out  by  Malus.  The  reader  who  is  desirous 
of  seeing  a  condensed  abstract  of  the  leading  mathematical  principles 
involved,  is  referred  to  a  brief  but  luminous  summary  drawn  up  by 
the  Eev.  A.  Neate,  M.  A.,  and  inserted  in  Professor  Powell's  Elemen- 
tary Treatise  on  Optics,  p.  71,  Oxford,  1833.  But  the  entire  subject 
has  been  treated  by  a  far  higher  analysis  with  extreme  generality,  and 
by  a  new  and  powerful  principle  of  his  own,  by  Sir  W.  E.  Hamilton, 
in  his  essay  on  the  Theory  of  Systems  of  Rays.  Mem.  of  R.  Irish  Acad- 
emy, vols.  XV.  and  xvi.,  and  Supplement,  vol.  xviii. —  Translator. 


140  MALUS. 

than  the  grounds  for  a  decision  between  the  claims  of  the 
two  rival  theories  of  light. 

The  celebrated  physicist  Wollaston,  some  years  before, 
had  proposed  a  method  by  means  of  which  to  deduce  the 
refractive  power  of  all  substances  whether  transparent  or 
opaque.  This  method  rests  on  the  determination  of  the 
angle  under  which  these  substances  applied  immediately 
in  contact  with  one  of  the  surfaces  of  a  prism  of  glass, 
through  which  we  look  at  them,  begin  to  cease  to  be 
A'isible. 

Now  according  to  the  theory  of  reflexion*  expounded 

*  To  render  what  follows  intelligible,  many  readers  may  find  it  per- 
haps desirable  if  we  here  exi^lain,  very  briefly,  the  view  of  ordinary 
reflexion  and  refraction  of  light  as  explained  respectively  by  the  emis- 
sion and  the  loave  theories. 

On  the  former  a  molecule  of  light  resembles  an  elastic  body,  which 
if  projected  obliquely  against  a  hard  plane  surface,  by  the  principles 
of  mechanics  rebounds  at  ore  anale  equal  to  that  at  which  it  im- 
pinged. 

In  refraction  the  investigation  is  more  difficult:  a  molecule  of  light 
is  here  supposed  to  enter,  projected  with  great  velocity,  among  the 
molecules  of  the  refracting  transparent  medium  which  are  at  such 
relative  distances  as  to  allow  it  freely  to  pass  among  them;  but  at  its 
first  entry  among  them  it  is  of  course  aitracled  by  them ;  it  then  be- 
comes a  problem  of  dynamics,  requiring  the  aid  of  the  higher  mathe- 
matics, to  determine  what  will  be  the  path  which  it  will  pursue  under 
their  influence.  In  general  it  is  clear,  that  under  these  united  attrac- 
tions urging  it  on,  its  velocity  will  be  accelerated:  but  to  go  into  the 
complete  solution,  would  be  beyond  the  limits  of  a  note.  It  was  fully 
investigated  by  Newton  {Principia,  lib.  i.  sect.  xiv.  prop.  94),  where 
he  demonstrates  that  on  these  principles  the  deviation  of  the  refracted 
ray  will  follow  the  law  that  the  sines  of  the  angles  of  incidence  and  re- 
fraction are  in  a  constant  ratio. 

Similar  investigations  have  been  pursued  by  Laplace,  more  espec- 
ially with  regard  to  atmospherical  refraction,  the  atmosphere  being 
supposed  to  consist  of  strata  of  different  densities.  {Mec.  Celeste,  vol. 
iv.  liv.  X.  ch.  i.  2,  3.) 

On  the  wave  hypothesis,  the  explanation  admits  of  a  very  simple 
kind  of  illustration. 


REFRACTIVE    POWER. 


141 


in  the^^lOth  hook  of  the  Mecaniqne  Celeste,  and  founded 
on  the  corpupfidar  hypothesis,  tlie  formulas  would  be  dif- 
ferent foi"  opaque  and  for  transparent  bodies.     It  is  on 

A  set  of  waves  propagnted  circularly  from  any  source,  when  they 
get  to  a  considerable  distance,  may  be  regarded  as  proceeding  in  par- 
allel planes.  In  all  cases,  the  portions  of  circles  or  spheres  which  are 
their  true  form  have  a  common  tangent  which  marks  what  is  called 
the  "front"  of  the  wave. 

But  whenever  waves  encounter  any  kind  of  obstacle,  or  enier  any 
new  medium,  then,  from  and  round  each  point  of  such  encounter,  a  new 
set  of  spherical  waves  begins  to  spread.  In  denser  media  these  new 
waves  spread  more  slowly  than  in  rarer,  but  when  the  obstacle  is  still 
surrounded  by  the  same  meiium,  then  the  velocity  is  unaltered. 

On  these  principles  the  ordinary  laws  of  reflexion  and  refraction  are 
proved  on  the  theory  of  waves. 

In  reflexion,  if  parallel  waves  u  u'  follow  at  equal  intervals  A,  u  im- 


pinging on  the  surface  at  o,  will  cause  a  new  circular  wave  to  spread 
backwards  from  that  point  as  a  centre;  when  the  next  wave  «' im- 
pinges at  o',  it  will  do  the  same,  and  so  on  in  succession.  But  when 
the  wave  from  o'  has  spread  to  a  radius  =2.,  that  from  o  will  have 
spread  to  a  radius  =2/1,  and  so  on.  Hence  to  these  contemporaneous 
circular  waves  drawing  a  common  tangent  v  v'  t  this  will  be  the  front 
of  the  reflected  waves,  and  the  radii  to  the  points  of  contact  o  v,  oi  vi, 
will  give  the  inclination  of  the  refected  rays,  which  is  easily  seen  to  be 
equal  to  that  of  the  incident,  since  ol  v'  =oi  u=2.,  and  a  v—2ol  v,  whence 
0  o'—oi  t,  and  the  triangles  upon  these  equal  bases  being  right-angled, 
the  angle  v  t  o=u  o  c',  or  the  angle  of  incidence,  is  equal  to  that  of 
reflexion. 


142 


MALUS. 


this  point  then,  they  would  say,  that  WoUaston  was  de- 
ceived. The  object  which  Malus  proposed  in  his  memoir 
was  to  submit  this  point  to  a  decisive  experimental  test. 
He  chose  a  substance,  beeswax,  whose  refractive  power 
could  be  measured  in  the  transparent  state,  and  in  the 
opaque  state  by  the  method  of  Wollaston.  He  applied 
to  the  angles  of  disappearance  corresponding  to  these  two 
conditions,  and  sufficiently  different  one  from  the  other, 
the  formulas  of  the  Mecanique  Celeste,  and  he  found  there 
would  result  refractive  powers  perfectly  identical.     This 

For  refraction ;  by  an  analogous   construction,  tlie  circles  which 


spi'ead  in  the  denser  medium  are  smaller  than  those  in  the  first,  the 
radii  being  diminished  in  the  ratio  of  the  velocities  or  inversely  as  the 
densities.  Thus  when  the  new  wave  originating  at  o'  has  spread  to  »/, 
that  from  o  will  have  spread  to  doiible  the  same  radius  at  v.  The  com- 
mon tangent  or  front  of  the  refracted  waves  will  be  inclined  at  an  angle 
0  t  V,  which  is  easilj^  determined  by  drawing  the  pai-allel  through  i  of 
the  incident  light,  whence  we  have  {i  and  r  being  the  angles  of  inci- 
dence and  :-efraction)  m  t=o  t  sin.  i,  and  o  v=o  t  sin.  r ;  but  o  v  and  u  t 
being  the  radii  of  waves  in  the  two  media,  are  in  the  constant  ratio  of 
the  densities  =fJ.;  hence  sm.  i  =("  sin.  »•,  which  is  the  experimental 
law  of  refraction. 


REFRACTIVE    POWER. 


143 


identity  of  the  refractive  powers  of  wax,  wben  transparent 
and  when  opaque,  which  seemed  to  be  a  necessary  result, 
appeared  both  to  tlie  author,  to  Laplace,  and  to  all  the 

The  law  of  refraction  may  also  be  more  briefly  deduced  thus :  tak- 
ing the  fronts  of  the  incident  and  refracted  rays  perpendicular  to  their 


directions,  their  inclinations  will  be  determined  by  the  relative  veloci- 
ties with  which  those  fronts  advance;  and  while  the  incident  front  has 
advanced  through  a  space  d,  that  of  the  refracted  will  have  advanced 
through  cZj  proportional  to  their  velocities;  or, 
d  V 


But  geometrically  for  any  breadth, 

d  =  b  sin.  i 
Hence, 


dT  =  b  sin.  r. 


fi     =     ■ , 

sin.  »• 
which  is  the  law  of  refraction. 

This  method,  though  in  a  less  concise  form,  is  given  by  Mr.  Power 
(  On  Absorption  of  Rays,  ^-c,  Pldlos.  Trans.  1854,  part  i.,)  who  never- 
theless calls  in  question  the  principle  of  the  assumption  that  the  front 
of  the  rays  is  stricth'-  perpendicular  to  their  direction,  and  proposes  a 
more  general  view:  from  which,  without  any  assumption  as  to  the 
nature  or  law  of  refraction,  he  shows  that  the  formula  of  the  sines  is 
directly  deducible  from  his  analysis.  Objections,  however,  have  been 
raised  against  his  reasoning. —  Translator. 


144  MALUS. 

mathematicians  and  physicists  of  the  Emission  School  in 
Europe,  to  afford  a  mathematical  proof  of  the  truth  of 
the  emission  theory.  It  is  assuredly  a  singular  thing  that 
there  should  be  this  perfect  identity  of  refractive  powers 
calculated  from  angles  of  disappearance  differing  from 
each  other,  and  according  to  formulas  very  dissimilar  be- 
tween themselves. 

But  what  proof  was  there  that  the  refractive  powers 
ought  to  be  identical?  Ought  we  to  suppose  that  the 
change  from  the  solid  to  the  fluid  state  in  any  substance 
would  be  without  influence  on  its  refractive  power? 
Might  we  not  cite  cases  in  which  heat  modifies  the  re- 
fractive power  of  bodies  independently  of  their  density  ? 
Again,  were  the  temperature  of  the  wax  and  its  density 
well  ascertained  at  the  moment  of  the  experiment  such 
as  Malus  was  obliged  to  make  it  ?  Besides,  would  it  be 
strange  to  suppose  that  within  those  limits  where  the 
action  of  bodies  on  light  opei'ates,  there  are  no  sub- 
stances truly  opaque ! 

Now  that  the  system  of  emission  is  overthrown  without 
hope  of  restoration,  I  endeavour  to  recall  all  the  circum- 
stances by  which  Malus  might  possibly  have  been  misled. 
But,  for  my  own  part,  I  feel  sure  that  I  do  not  deceive 
myself  in  affirming  that  the  memoir  of  which  we  are 
speaking  offers  a  new  proof  of  the  mathematical  spirit 
and  experimental  talent  which  Malus  possessed  in  so 
high  a  degree.  We  ought  only  to  regret  that  the 
conclusions  in  the  report  were  so  explicit  that  they 
represented  the  atomic  theory  of  light  as  completely 
established  ;  and  that  such  a  decision,  emanating  from 
individuals  so  competent  as  Laplace,  Haiiy,  and  Gay- 
Lussac,  may  perhaps  have  contributed  to  alienate  our 
illustrious  associate  from  that  experimental  path  which 


EMISSION    AND    "WAVE    THEORIES. 


145 


Fresnel  a  few  years  afterwards  showed  to  be  so  astonish- 
ingly fruitful  in  results.* 

*  In  the  remarks  here  made  by  Arago  on  Malus's  investic;ation  of 
the  refractive  powers  of  solid  and  liquid  wax,  there  appears  some  lit- 
tle obscurit}'  of  statement,  and  a  degree  of  importance  attached  to  the 
result  as  decisive  between  the  rival  theories,  which  it  does  not  appear 
to  deserve. 

Perhaps  for  the  general  reader  a  few  words  explanatory  of  the 
method  may  be  necessary,  in  order  to  see  the  general  bearing  of  the 
case. 

When  a  ray  passes  out  of  a  denser  medium  m  into  a  rarer  n,  the 
angle  of  refraction  r  will  be  greater  than  that  of  incidence  /,  according 
to  the  well-known  law  of  the  sines,  which  liere  becomes  sin  r=u 
sin  i.     But  /i  being  constant  for  the  same  two  substances,  there  is  a 

1 
certain  limit  to  i  when  sin    r=l  or  r=90°  or  sin  i=-  that  is,  the 

refracted  ray  coincides  with  the  bounding  surface  of  the  media,  or  it 
ceases  to  be  refracted:  and  if  i  exceed  tiiis  value,  sin  r  would  be 
greater  than  unity,  which  is  impossible,  or  the  ray  cannot  emerge  from 
the  denser  medium,  but  must  remain  wholly  within  it.  This  alone, 
however,  does  not  prove  that  it  will  be  reflected.     Experiment,  how- 


ever, shows  that  it  is,  and  the  precise  angle  i  at  whicli  this  beo-Ins  to 

1  ° 

take  place,  or  when  sin  i=  -  for  any_;joJ;'  of  media,  can  bo  easily  and 

accurately  determined;  thus  ji  is  found  for  that  pair  of  substances 
but  It  is  the  compound  ratio  of  the  separate  refractive  powers  of  each 
out  of  vacuum  or  air;  if,  therefore,  one  of  these  is  known,  the  other 
is  deduced. 

On  this  principle  Dr.  Wollaston's  method  was  founded  (P/«7.  Trans. 

SEC.   SER.  7 


146  MALUS. 

1802).     Any  substance  n,  of  less  refractive  power  than  glass  in  opti- 
cal contact  with  the  base  of  a  glass  prism  m,  can  be  seen  by  an  ej'e 


at  e  at  any  incidence  within  the  limit  just  mentioned,  or  while  the  ray 
i  entering  the  other  side  of  the  prism  and  impinging  on  its  base,  is  in- 
capable of  being  refracted  out  at  the  base,  and  therefore  reflected  from 
within;  but  as  soon  as  this  limit  is  exceeded,  or  the  ray  is  refracted 
out  at  the  base,  then  n  ceases  to  be  visible  at  e.  The  exact  incidence 
or  "  critical  angle  "  at  ■which  this  takes  place,  is  measured  by  an 
appropriate  apparatus,  and  the  refractive  index  for  n  deduced,  that  of 
the  prism  being  known,  a  series  of  substances  being  applied  in  suc- 
cession, whether  transparent  or  opaque.  Dr.  Wollaston  in  this  way 
determined  their  refractive  indices.  As  the  different  primary  rays 
have  indices  a  little  differing,  and  which  are  greatest  for  red  light,  Dr. 
Young  remarked  that  the  limit  thus  found  applies  in  strictness  to  the 
extreme  red  ray. 

In  this  way  Dr.  Wollaston  found  the  refractive  indices  as  follows: — 
White  wax,  boiling         -  -  .  1.542 

Ditto  cold      -  -  -  -      1.535 

In  the  same  way  ]\Ialus  found 

Waxat  14°  Reaum.  (=63^  Fahr.)      -  -  1.5123 

Ditto  melting  ...       1.4503 

Ditto  boiling       -  -  -  1.4416 

(These  numbers  are  all  lower  than  the  former,  probably  from  a  dif- 
ferent sort  of  wax  being  used.) 

Dr.  Wollaston,  in  applying  the  simple  calculation  above  indicated 
to  the  observed  angles,  did  not  question  the  vei-y  natural  assumption, 
that  the  same  Ibrmulas  would  apply  to  the  observed  angles  equally, 
whether  the  substance  was  opaque  or  transparent,  solid  or  fluid. 

Laplace,  in  a  theoretical  investigation  founded  on  certain  consider- 
ations derived  from  the  molecular  theory,  framed  his  formulas  on  the 
assumption  that  the  conditions  were  different  for  opaque  and  for 
transparent  bodies,  and  even  for  the  same  substances  in  the  two  states 
respectively.  The  que;.tion  at  issue  was  the  truth  of  this  assump-  - 
tion,  though  it  must  be  confessed  that  little  appears  in  the  tenth  book 


DOUBLE  REFRACTION.  147 

MALUS  GAIXS  THE  PRIZE  PROPOSED  BT  THE  ACAD- 
EMY FOR  A  MATHEMATICAL  THEORY  OF  DOUBLE 
REFRACTION. 

On  the  4tli  January,  1808,  the  Academy  proposed,  as 
the  subject  for  a  prize  in  physical  science  to  be  decided 
in  1810,  the  following  question  : — 

"  To  give  a  mathematical  theory,  confirmed  by  experi- 
ment, of  the  double  refraction  which  light  undergoes  in 
passing  through  diiferent  ci'ystallized  bodies." 

The  memoir  of  Malus  received  the  prize.  Doubtless 
fearing  lest  he  should  be  forestalled  by  some  of  the  com- 
petitors, in  the  discovery  of  the  singular  properties  of 
light  which  he  had  observed,  this  eminent  physicist  com- 
municated the  most  essential  parts  of  his  researches  to 
the  Academy  on  the  12th  December,  1808,  without 
waiting  for  the  period  at  which,  according  to  the  pro- 
gramme, the  competition  was  to  be  closed.  It  is  then  to 
the  end  of  the  year  1808  that  the  immortal  discoveries 
belong  of  which  I  proceed  immediately  to  give  you  an 
analysis.  The  commission  appointed  to  judge  of  the  com- 
petitors was  composed  of  Lagrange,  Haiiy,  Gay-Lussac, 

of  the  Mec.  Celeste  by  which  this  conclusion  can  be  considered  as 
established. 

Malus  observed  by  Wollaston's  method  the  angles  at  which  the  dis- 
appearance took  place  in  wax,  solid  and  in  fusion.  Tliese  angles  were 
different;  and  calculated  in  the  usual  way,  the  indices  of  refraction 
resulted  different  also  (as  seen  in  the  above  tabular  view). 

The  same  observed  angles,  however,  calculated  b}'  Laplace's  for- 
mula gave  the  resulting  index  the  same  in  both  cases. 

Now  Laplace,  Malus,  and  the  emissiouists,  considered  the  identity 
of  refractive  power  thus  resulting  to  be  a  necessary  truth — why  so,  we 
do  not  see;  it  is  obviously,  at  best,  a  mere  consequence  of  the  assump- 
tion made  at  the  first.  The  result  is  no  proof  of  its  truth,  and  decides 
nothing  either  way.  Arago's  laboured  remarks  therefore  seem  super- 
fluous.—  Translator. 


148  MALUS. 

and  Biot.  The  report  was  presented  by  Lagrange,  and 
thus  nothing  was  wanting  duly  to  signalize  the  important 
discovery  of  Malus. 

DISCOVERY    OF    POLARIZATION   BT   REFLEXION. 

.  We  must  go  back  to  Erasmus  Bartholimus  to  find  the 
first  observations  relative  to  the  existence  of  double 
refraction  in  Iceland  spar,  also  called  calc  spar,  or  rhom- 
boidal  carbonate  of  lime.  Huyghens  had  occupied  him- 
self with  the  study  of  these  phenomena,  and  pointed  out 
a  geometrical  construction  of  a  very  simple  and  elegant 
kind  by  which  we  can  determine,  in  all  directions  and  at 
all  incidences,  the  position  of  the  extraordinary  ray  rela- 
tive to  the  ray  properly  called  the  ordinary  ray,  whose 
position  is  determined  by  the  well-known  law  of  the 
sines,  made  known  by  Descartes.  Huyghens  arrived  at 
the  discovery  of  this  construction  by  means  of  an  ellip- 
soid, which,  as  he  tells  his  readers,  he  derived  from  con- 
siderations borrowed  from  the  theory  of  waves. 

The  reporter  of  the  Academy  on  Malus's  memoir  of 
the  12th  December,  1808,  entitled  Memoir  on  a  Prop- 
erty of  Light  reflected  hy  transparent  Bodies,  who  was 
no  other  than  Laplace,  wished  that  Huyghens  had  been 
contented  to  have  given  his  law  as  the  result  of  experi- 
ence only.  But  I  may  be  permitted  to  ask.  Is  not  the 
hatred  of  theory  carried  too  far  when  it  leads  to  the  sug- 
gestion of  dissimulation  or  the  want  of  sincerity  ? 

Newton  contended  for  substituting  other  rules  instead 
of  that  of  Huyghens  ;  but  these  have  not  been  found 
conformable  to  facts. 

Among  modern  observers,  "Wollaston  was  the  first  who 
established  the  truth  of  the  principles  laid  down  by  the 
Dutch  philosopher.     To  make  this  verification  he  availed 


DOUBLE    REFRACTION.  149 

himself  of  the  ingenious  method  by  which  he  found  the 
index  of  refraction  by  means  of  total  reflexion.  It  ap- 
pears that  in  1808  these  verifications  had  not  appeared 
sufficient  to  the  physicists  of  the  Academy  of  Sciences, 
since  they  proposed  the  question  as  the  subject  of  a  prize 
for  experimenters.  However  this  may  have  been,  Malus 
translated  the  construction  of  Huyghens  into  analytical 
formulas :  he  compared  the  deviation  of  the  extraordi- 
nary rays  deduced  from  these  formulas  with  the  numbers 
resulting  from  very  accurate  observations,  and  the  accord- 
ance was  in  all  cases  very  perfect.  Thus  the  geomet- 
rical conception  of  Huyghens  was  found  to  be  completely 
established,  although  originally  the  author  was  led  to  it 
by  theoretical  views. 

A  ray  of  light  divides  itself  into  two  rays  which  are  of 
exactly  the  same  intensity  whatever  be  the  position  of 
the  crystal  which  it  traverses,  and  in  which  the  division 
into  two  is  produced.  But  the  case  is  different  when  the 
rays  pass  out  of  one  crystal  and  are  received  into,  and 
analyzed  by,  a  second  crystal  exactly  similar.  If  this  sec- 
ond crystal  is  situated  relatively  to  the  first  in  such  a  way 
that  the  corresponding  faces  ai-e  respectively  parallel  to 
each  other,  the  ordinary  ray  in  traversing  it  only  under- 
goes the  ordinary  refraction,  and  the  extraordinary  ray 
also  remains  exclusively  an  extraordinary  ray.  The 
natural  light  then  in  traversing  the  first  crystal  has  thus 
changed  its  nature.  In  fact,  if,  in  becoming  double,  it 
had  preserved  its  original  properties,  the  ordinary  ray 
and  the  extraordinary  would  each  have  been  divided  into 
two  rays  in  traversing  the  second  crystal.  At  emer- 
gence from  the  second  crystal  we  should  have  had  four 
images  instead  of  two.  The  first  idea  which  occurs  to 
the  mind  would  be  that  the  natural  light  is  composed  of 
parts  which  are  susceptible,  some  of  them  undergoing  the 


150  MALUS. 

ordinary,  some  the  extraordinarj,  refraction,  and  an 
equal  number  of  each.  But  this  hypothesis  is  radically 
subverted  by  a  very  simple  experiment. 

If  we  cause  the  second  crystal  to  turn  through  one 
fourth  of  a  revolution  round  itself,  retaining  the  paral- 
lelism of  its  upper  and  under  surfaces  to  those  of  the 
first,  the  ordinary  ray  will  now  become  extraordinary, 
and  the  extraordinary  will  now  undergo  only  the  ordi- 
nary refraction.* 

*  The  subject  of  double  refraction,  of  which  the  most  characteristic 
results  are  here  stated  by  the  author,  is  one  which  is  rarely  made  in- 
telligible to  a  general  reader  by  a  mere  cursory  description,  and  with- 
out going  into  some  detail  of  the  successive  changes  which  result  on 
receiving  the  two  rays  emitted  from  one  crvstal  of  calc  spar  on  to 
another  placed  in  successively  varied  positions  with  respect  to  the 
first.  Perhaps  few  points  are  however  easier  to  exhibit  experimen- 
tally— which  affords  by  far  the  readiest  way  of  familiarizing  ourselves 
with  the  whole  phenomenon  and  its  laws.  It  is  only  necessary  to 
procure  two  moderately  clear  rhombs  of  calc  spar,  and  attach  to  the 
side  of  one  of  them  a  card  containing  a  small  hole  at  the  centre.  It  is 
then  easy  to  look  through  the  two  crystals  at  the  light  admitted 
through  the  small  hole;  and  keeping  the  two  crystals  with  their  sui-- 
faces  in  contact,  the  one  next  the  eye  can  be  turned  round  so  that  its 
angles  point  in  different  directions  with  respect  to  those  of  the  other. 
For  this  purpose,  by  far  the  most  convenient  arrangement  is  to  fix  the 
two  crystals  in  small  tubes  (such  as  card  pill-boxes),  which  can  turn 
one  in  the  other:  and  if  the  crystals,  and  consequently  the  hole,  be 
small  (for  the  images  not  to  overlap),  it  is  very  convenient  to  magnify 
the  images  by  a  small  lens  fixed  in  the  tube  next  the  eye,  so  that  the 
object  to  be  viewed  in  focus  is  the  small  hole  at  the  farthest  surface 
of  the  second  crystal.  The  series  of  clianges  are  these:  setting  out 
from  a  position  in  which  the  two  rhombs  are  similarly  situated,  (as  if 
parts  of  one  larger  crystal,)  there  are  two  images  well  separated. 
These  are  represented  at  b  in  the  figure  (the  two  at  A  being  drawn 
for  comparison  when  only  one  rhomb  is  used).    Now,  making  one 


A      B 

C 

D 

E 

T-         G 

n 

T 

IL 

® 

«_ 

•  * 

s 

•e 

o 

DOUBLE    REFRACTION.  151 

Thus,  then,  the  two  rays  on  emerging  from  the  first 
crystal,  instead  of  being  changed  in  their  nature,  are  ex- 
actly alike  ;  it  suffices,  to  show  them  undistinguishable 
from  each  other,  to  make  one  of  these  rays  turn  round 
the  line  of  its  own  direction  through  90°.  Thus  we  are 
brought  by  the  phenomena  of  double  refraction  to  distin- 
guish in  rays  of  light  different  sides  endowed  with  dif- 
ferent properties.  We  are  brought  by  observation  to 
acknowledge  that  the  extraordinary  ray  emerging  from  a 

rhomb  revolve  continuously,  we  haxQ  four  images  (as  at  c)  unequally- 
bright  by  pairs:  at  45°  four  equally  bright  (d),  the  other  pair  now  be- 
come faint  (e),  until  at  90°  they  are  reduced  to  two,  (f).  The  same 
changes  are  repeated  at  g  and  h;  when  at  135°  the  four  are  equally 
bright,  till,  after  two  become  faint  at  i,  we  arrive  at  180°,  where,  as 
at  K,  the  two  brighter  coalesce  into  one.  The  same  changes  then 
take  place  in  reverse  order;  four  images  at  225°,  two  at  270°,  four  at 
315°,  and  lastly  two  at  860'. 


To  give  any  idea  of  the  analysis  of  these  phenomena,  it  is  necessary 
in  the  first  instance  to  observe  accurately  the  form  of  the  crystal,  and 
obtain  a  distinct  idea  of  the  terms  the  axh  and  the  principal  section  of 
the  crystals,  wliich  will  be  understood  at  once  by  the  aid  of  the  an- 
nexed diagram ;  where  taking  the  short  diagonal  of  two  of  the  oppo- 
site faces  of  the  crystal,  as  A  D,  the  plane  passing  through  it  A  D  x,  is 
the  principal  section,  and  the  diagonal  of  that  plane  A  x,  the  axis  of 
the  crystal.  The  double  refraction  of  a  ray  r  is  represented  by  its 
division  into  two  raj's,  o  the  ordinarj',  and  e  the  extraordinary. 

Whatever  theory  we  adopt  as  to  the  nature  of  light,  the  phenomena 
can  only  be  explained  bj-  supposing  a  section  of  each  of  the  rays 


152 


MALUS. 


crystal  of  Iceland  spar,  lias  the  properties  of  an  ordinary 
ray  if  we  only  make  it  turn  round  itself  through  a  quar- 
ter of  a  revolution. 

■within  the  crystal  to  be  of  an  elon  gat  ecUorm;  it  maybe  represented 
by  a  short  straight  line,  as  o  and  e  in  the  annexed  figure  (1.):  if  the 


Fiff.  2. 


Fig.  1. 


rhomb  represent  a  section  of  the  crystal  looking  down  perpendicu- 
larly upon  it,  and  snpposing  the  light  to  fall  on  it  in  the  same  perpen- 
dicular line,  s  s  will  be  the  projection  of  its  principal  section,  and  the 
short  lines  o  and  e  will  be  the  projections  of  the  sections  of  the  ordi- 
nary and  extraordinary  rays. 

Now  let  \is  conceive  this  first  crystal  to  retain  its  position,  and  its 
principal  section  s  s  to  remain  parallel  to  itself,  as  in  Jig.  2,  and  a 
second  crystal  placed  upon  it,  having  its  principal  section  s'  s'  in- 
clined at  any  angle  to  the  former;  then  supposing  the  sections  o  and 
E  to  renaain  as  before,  relatively  to  s  s,  that  is  one  parallel,  and  the 
other  perpendicular  to  it,  when  those  rays  enter  the  second  crystal, 
the  effect  is  that  they  can  only  pass  through  it  in  such  portions  as  are 
either  parallel  or  perpendicular  to  its  principal  section  si  s'.  It  be- 
comes then  simply  a  case  of  resolution  of  motions,  represented  by  the 
lines  o,  e,  and  it  seems  nearly  impossible  to  imagine  this  without 
associating  it  with  vibrations.  At  all  events,  the  only  way  of  con- 
ceiving the  matter  is  to  admit  that  in  some  way  o  is  simply  resolved 
into  two  components  at  right  angles;  one  in  the  plane  si  si,  the  other 
perpendicular  to  it,  which  are  represented  by  o„  and  o^  In  like 
manner  e  is  resolved  into  e^  parallel  to  s'  s',  and  e^  perpendicular  to 
it.     According  to  the  inclination  given  to  s'  s',  relative  to  s  s,  the 


DOUBLE    REFRACTION.  153 

If  we  call  to  mind  that  rays  of  light  are  so  immensely 
attenuated  that  myriads  of  them  can  pass  through  the 
eye  of  a  needle  without  mutual  disturbance,  reflecting 
minds  will  recognize  how  much  there  is  most  admirable 
and  almost  incomprehensible  in  the  fact  which  we  have 
just  cited,  the  discovery  of  which  is  also  due  to  Huy- 
ghens.  The  two  pencils  of  rays  which,  after  emergence 
from  the  crystal  of  Iceland  spar,  have  sides  endued  with 
different  properties,  are  called  rays  "  polarized  "  in  con- 
tradistinction to  rays  of  natural  light,  possessing  the  same 
property  all  round  their  circumference,  since  tbey  sepa- 
rate into  two  beams  of  the  same  intensity  in  whichever 
direction  their  sides  may  lie  with  respect  to  the  form  of 
the  crystal  with  which  they  are  analyzed.  I  have  men- 
tioned what  ought  to  be  the  position  of  a  second  crystal, 
so  that  the  ordinary  and  extraordinary  rays  emerging 
from  the  first  crystal  may  preserve  respectively  the  same 
denominations.  In  the  intermediate  positions  of  the  sec- 
ond crystal,  the  rays,  whether  ordinary  or  extraordinary, 
coming  from  the  first,  in  general  divide  themselves  each 
into  two,  but  the  intensities  of  the  two  portions  are  ordi- 
narily very  different. 

changes  in  magnitude  in  these  resolved  parts  will  give  the  relative 
brightness  of  the  images. 

Rays  whose  sections  are  represented  as  in  the  figure,  are  said  to  be 
polarized  in  the  planes  of  o  and  e  respectively;  but  it  was  long  a  dis- 
puted question  whether  the  vibrations  of  which  they  consist,  according 
to  the  wave  theory,  are  actually  performed  in  those  planes,  or  perpen- 
dicular to  them ;  the  latter  has  now  been  shown  to  be  the  fact. 

It  need  hardly  be  added  that  this  can  be  considered  only  as  a  very 
general  and  popular  kind  of  illustration ;  and  for  the  more  exact  state- 
ment cf  the  laws  of  these  changes,  especially  with  regard  to  the  rela- 
tive distances  of  the  several  images,  or  differences  of  ordinary  and 
extraordinary  refraction,  recourse  must  be  had  to  more  profound 
mathematical  investigations.  See  especially  Herschel  on  Light,  art. 
785,  el  seq. —  Tramlalor. 

7  * 


154 


MALUS. 


Such  was  the  state  of  our  knowledge  on  this  delicate 
and  singular  branch  of  optics,  when,  one  day,  in  his 
house  in  the  Rue  d'Enfer,  ]\Jalus  happened  to  examine 
through  a  doubly  refracting  crystal,  the  rays  of  the  sun 
reflected  by  the  glass  panes  of  the  windows  of  the  Lux- 
embourg Palace.  Instead  of  the  two  bright  images 
which  he  expected  to  see,  he  perceived  only  one, — the 
ordinary,  or  the  extraordinary,  according  to  the  position 
which  the  crystal  occupied  before  his  eye.  This  singular 
phenomenon  struck  him  much  ;  he  tried  to  explain  it  by 
supposing  some  particular  modifications  which  the  solar 
light  might  undergo  in  traversing  the  atmosphere.  But 
when  night  came,  he  caused  the  light  of  a  taper  to  fall 
on  the  surface  of  water,  at  an  angle  of  36°,  and  found, 
by  the  test  of  a  double  refracting  crystal,  that  the  light 
reflected  from  the  water  was  also  polarized,  just  as  if  it 
had  emerged  from  a  crystal  of  calc  spar.  The  same 
experiment  made  with  a  glass  reflector  at  the  incidence 
of  about  35°,  gave  the  same  result.  From  that  moment 
it  was  thus  proved  that  double  refraction  is  not  the  sole 
means  of  polarizing  light,  or  of  making  it  lose  the  prop- 
erty of  dividing  itself  constantly  into  two  pencils  on 
traversing  calc  spar.  Reflexion  at  the  surface  of  trans- 
parent bodies — a  phenomenon  occurring  every  instant, 
and  as  ancient  as  the  world — possessed  the  same  prop- 
erty, without  being  hitherto  suspected  by  any  one.  Ma- 
lus,  however,  did  not  stop  here  ;  he  caused  an  ordinary 
and  an  extraordinary  ray  from  calc  spar  to  fall  simulta- 
neously on  the  surface  of  water,  and  observed  that  at  the 
incidence  of  36°  these  two  rays  acted  in  a  very  different 
manner. 

When  the  ordinary  ray  underwent  a  partial  reflexion, 
the  extraordinary  ray  was  not  reflected  at  all, — that  is, 


DISCOVERY    OF    POLARIZATION.  155 

traversed  the  liquid  undiminished.  If  the  position  of 
the  crystal  was  such,  relatively  to  the  plane  in  which 
the  reflexion  took  place,  that  the  extraordinary  ray  was 
partially  reflected,  then  it  was  the  ordinary  ray  which 
was  entirely  transmitted. 

The  phenomena  of  reflexion  become  thus  a  means  of 
distinguishing  from  each  other  rays  polarized  in  opposite 
directions.  On  the  evening  which  followed  the  chance 
observation  of  the  sun's  light,  reflected  from  the  windows 
of  the  Luxembourg,  Malus  created  one  of  the  most 
remarkable  branches  of  modern  optics,  and  acquired  the 
title  which  no  one  will  ever  contest  to  an  immortal 
renown. 

I  should  exceed  the  limits  prescribed  me,  if  I  were 
here  to  analyze  all  the  observations  which  our  colleague 
made,  in  tracing  the  course  of  the  direct  and  reflected  rays 
in  which  the  phenomena  of  polarization  were  developed. 
But  I  cannot  omit,  in  order  to  prepare  the  reader  for 
understanding  the  curious  facts  with  which  Malus  en- 
riched the  science  in  1811,  to  give  the  definition  of  a 
term  which  I  shall  have  occasion  to  employ,  that  of  a 
ray  "  partially  polarized." 

A  ray  of  natural  light  always  gives  two  images  of  the 
same  intensity,  whatever  may  be  the  position  of  the  face 
of  the  crystal  wliich  it  traverses,  relatively  to  this  ray. 
A  ray  completely  polarized,  only  gives  one  image  in  two 
particular  positions  of  the  face  of  the  crystal.  A  ray 
partially  polarized,  possesses  in  some  sort  properties 
intermediate  to  those  of  the  natural  and  the  completely 
polarized  ray.  Like  the  natural  ray,  it  gives  always 
two  images  ;  and  as  with  the  polarized  ray,  these  two 
images  have  variable  intensities,  according  to  the  posi- 
tion of  the  analyzer.     Rays  i-eflected  from  water  or  from 


156  MALUS. 

glass,  at  angles  greater  or  less  than  that  of  complete 
polarization,  are  partially  polarized,  and  in  a  greater 
degree,  as  their  inclination  to  the  reflecting  surface 
approaches  nearer  to  35°  or  36°  respectively. 

Mains  conceived  that  rays  reflected  from  metals  are 
not  polarized  even  partially  ;  but  this  was  a  slight  error 
which  was  soon  after  rectified. 

After  his  first  researches,  Malus  believed  that  re- 
flexion from  certain  transparent  and  opaque  substances, 
besides  double  refraction,  was  the  sole  means  of  polariz- 
ing light.  About  the  end  of  the  year  1809,  his  views  on 
this  subject  underwent  a  great  extension  ;  he,  in  fact, 
recognized,  experimentally,  that  light  which  has  passed 
through  a  plate  of  glass,  shows  at  certain  inclinations 
evident  traces  of  partial  polarization  ;  and  that  if  we 
form  a  pile  of  glasses,  the  natural  ray  which  traverses 
them  emerges  completely  polarized. 

He  did  not  fail  to  remark,  that  the  polarization  of  the 
ray,  in  this  case,  was  the  opposite  to  that  with  which  the 
reflected  ray  under  the  same  circumstances  Avas  aflPected  ; 
so  that  if  the  latter  were  identified  with  the  ordinary 
ray,  emerging  from  a  crystal  placed  in  a  given  position, 
the  former,  i.  e.  the  ray  passing  through  the  pile  of  glass 
plates,  would  be  similar  to  the  extraordinary  ray  of  the 
same  crystal. 

It  does  not  enter  into  our  plan  to  point  out  either  the 
detailed  and  very  curious  consequences  which  Malus 
deduced  from  his  experiments,  or  the  further  improve- 
ments they  have  received.  I  shall  content  myself  by 
here  saying  that  whenever  we  find  a  substance  which 
alone,  at  the  angle  of  complete  polarization,  reflects  one 
half  of  the  incident  light,  the  ray  transmitted  through  a 
single  plate  will  also  be  completely,  instead  of  partially, 


CONSEQUENCES    OF   POLARIZATIOX.  157 

polarized.  We  have  no  longer  need,  in  order  to  obtain 
tliis  complete  polarization  by  refraction,  to  resort  to  a 
pile  of  glasses  as  Mains  did  ;  a  single  plate  will  suffice.* 
After  the  experiments  of  Huyghens  on  the  double 
refraction  of  Iceland  spar  and  of  rock  crystal,!  mineralo- 
gists recognized  that  there  exists  in  nature  a  great  num- 

*  The  statement  which  Arago  here  gives  as  to  the  complete  polari- 
zation of  a  ray  by  transmission  through  a  single  plate,  is  a  result  of 
the  theoretical  investigations  of  Fresnel;  being  in  fact  only  a  particu- 
lar case  of  one  of  his  general  formulas  whicli  include  the  whole  the- 
ory of  polarization,  both  complete  and  partial. 

According  to  Fresnel's  principle,  common  light  is  equivalent  to  a 
combination  of  two  rays  of  equal  intensity,  polarized  in  planes  at 
right  angles  to  each  other.  At  reflexion  each  component  gives  a 
reflected  and  a  refracted  ray,  which,  again,  are  in  phones  at- right 
angles  to  each  other;  but  in  these  rays  in  the  re/?ec<ec?  pencil  it  fol- 
lows, from  Fresnel's  formulas,  that  the  portion  polarized  in  the  plane 
of  incidence,  will  always  be  of  greater  intensity  than  the  other,  and 
the  excess  will  show  itself  in  the  j^c^rtially  polarized  character  of  the 
reflected  ray  at  all  incidences;  and  in  the  refracted  ray  there  will  in 
like  manner  always  be  an  excess  polarized  in  the  plane  at  right 
angles  to  that  of  incidence.  This  excess  changes  with  the  incidence. 
At  the  angle  of  complete  polarization  the  ichole  of  the  reflected  ray  is 
polarized,  but  as  this  amounts  to  one  half  the  incident  ray,  the  re- 
maining half  which  is  transmitted  is  also  wholly  polarized  in  the 
rectangular  plane. —  Translator. 

t  As  the  discovery  of  the  very  small  double  refractive  power  of 
rock  crystal  has  been  sometimes  ascribed  to  later  experimenters,  it 
may  be  interesting  to  give  the  passage  in  which  Huyghens  describes 
his  owQ  observations  of  it. 

He  remarks,  that  his  theory  seems  more  probable  "  from  certain 
phenomena  which  I  have  observed  in  ordinary  crystal  ivJiich  grows  in 
a  liexagonal  form,  and  which,  in  consequence  of  this  regularity,  seems 
also  to  be  composed  of  particles  of  a  certain  figure,  and  regularly  dis- 
posed. This  crystal  has  a  double  refraction,  as  well  as  Iceland  spar, 
though  less  evident.  In  cutting  it  into  prisms  by  different  sections,  I 
remarked  that  in  all,  looking  through  them  at  tlie  flame  of  a  candle, 
or  the  leaden  divisions  of  a  casement,  they  appeared  double,  though 
with  images  veiy  little  separated;  whence  I  saw  the  reason  whj'  this 
body,  though  so  very  transparent,  is  useless  for  telescopes  when  they 
are  of  any  great  length,"  Traite  sur  la  Lumiere,  ch.  v.  ^  20. —  Trans- 
lator. 


158  MALUS. 

ber  of  crystals  endowed  with  double  refraction  ;  but 
when  a  crystal  was  proposed  for  examination,  there  was 
no  way  of  determining  whether  it  could  be  classed  among 
this  description  of  crystals,  until  after  it  had  been  cut 
into  a  prism,  and  trial  made  whether  the  image  of  a  very 
narrow  body,  such  as  the  point  of  a  needle,  would  be 
double,  seen  through  tbe  two  inclined  surfaces,  whether 
artificial  or  natural  But  in  1811  a  member  of  the 
Academy*  showed  that  it  was  possible  to  decide  such 
questions,  without  being  restricted  to  the  proof,  often 
very  difficult,  of  doubling  the  image.  He  proved  thus 
the  existence  of  double  refraction  in  the  thinnest  plates  of 
mica,  which  could  in  no  way  have  been  subjected  to  the 
former  mode  of  examination.  Malus  generalized  the 
results  thus  obtained  by  his  friend,  in  a  memoir  entitled. 
On  the  Axis  of  Refraction  of  Crystals  and  Organized 
Substances,  read  to  the  Academy  August  19,  1811. 

LETTER    FROM    YOUNG    TO    MALUS. 

On  the  22d  of  March,  1811,  Dr.  T.  Young  wrote  to 
Malus,  in  terms  of  great  courtesy,  to  inform  him  that  the 

*  Arago  here  nlludes  to  his  own  discovery  of  the  polarized  tints 
displayed  by  any  plate  of  a  doubly  refracting  crystal  when  interposed 
between  the  polarizing  and  the  analyzing  parts  of  the  apparatus.  By 
this  means  the  eye  recognizes  at  once,  by  the  appearance  of  colour,  the 
existence  of  double  refraction  in  that  crystal  plate  which  might  be  far 
too  minute  in  the  deviation  of  images  it  would  give  to  be  detected  by 
the  nicest  observation ;  as  well  as  the  existence  of  polarization  in  any 
light  examined  by  this  test.  It  was  thus  that  Arago  detected  polari- 
zation in  the  light  of  comets,  proving  that  thej^  shine  by  reflexion. 

The  same  principle  might  be  applied,  to  distinguish  on  inspection  a 
sm&WJixed  star  from  an  asteroid,  and  thus  probably  enable  astrono- 
mers rapidly  to  discover  more  of  those  bodies,  were  it  not  that  all 
known  forms  of  polarizing  apparatus  necessarily  involve  so  great  a 
loss  of  light,  that  the  method  would  probably  be  inapplicable  to  such 
faint  objects. —  Tnindntor. 


LETTER    FROM    YOUNG    TO    MALUS.  159 

Council  of  the  Royal  Society  of  London  had  awarded  to 
him  the  Rumford  Medal. 

So  little  was  the  progress  which  had  been  made  in 
England  in  these  new  theories,  that  Young  requested 
Malus  to  assure  him  whether  a  ray  polarized  by  reflexion 
from  glass,  was  really  not  reflected  by  a  second  glass 
suitably  placed,  as  Malus  had  announced.  In  the  opinion 
of  the  learned  Secretary  of  the  Royal  Society,  the  rays 
which  after  a  first  reflexion  were  incapable  of  reflexion 
at  a  second  surface  ought  to  be  absorbed  or  rendered  inert. 

Again  we  read  in  this  same  letter :  "  Your  experi- 
ments demonstrate  the  insufficiency  of  a  theory  (that  of 
interferences)  which  I  had  adopted,  but  they  do  not  prove 
its  falsity." 

Malus,  who  was  a  declared  and  immovable  partisan  of 
the  theory  of  emission,  accepted  with  great  joy  the 
declaration  of  Young  on  the  insufficiency  of  the  doctrine 
of  interferences.  He  always  held  out  the  opinion  of  the 
celebrated  Secretary  of  the  Royal  Society  to  those  who 
entreated  him  to  examine,  with  his  superior  genius,  the 
hypothesis  in  favour  of  Avhich  such  men  as  Huyghens 
and  Euler  stood  so  openly  committed.  He  did  not 
remark  that  Young,  in  admitting  the  insufficiency  of 
that  theory  in  1811,  had  the  caution  to  add  that  nothing 
up  to  that  time,  even  after  the  discovery  of  polarization, 
had  proved  its  falsity.* 

*  It  may  illustrate  further  the  want  of  due  appreciation  of  the  value 
of  Malus's  discovery  on  its  first  announcement,  if,  besides  the  letter 
of  Young  here  quoted,  we  refer  to  several  other  passages  in  his  cor- 
respondence, from  which  it  appears  how  entirely  the  discovery  of 
polarization  was  regarded  as  something  if  not  quite  at  variance  with 
the  theory  of  waves,  yet  as  wholly  incapable  of  representation  by  its 
principles. 

Young,  himself,  went  so  far   as  to  predict  that  it  was  a  problem 


160 


MALUS. 


INVENTION    OP    THE    REPEATING    GONIOMETER. 

Physical  theories   and  experimental  methods  have  a 
mutual  reaction  on  each  other.     The  former  cannot  be 

which  "  would  probably  long  remain   to  mortify  the  vanity  of  an 
ambitious  philosophy,  completely  unresolved  by  any  theory." 

Again,  in  a  review  of  Malus's  paper  (in  1811),  he  considers  it  "  con- 
clusive with  respect  to  the  insufficiency  of  the  undulatory  theory  in  its 
present  state,  for  explaining  all  the  phenomena  of  light."  And  again, 
in  a  letter  to  Sir  David  Brewster,  five  years  later,  he  expresses  himself 
thus:  "  With  respect  to  my  fundamental  hypotheses  respecting  the 
nature  of  light  (i.  e.  the  wave  theory),  I  become  less  and  less  fond  of 
dwelling  on  them,  as  I  learn  more  and  more  facts  like  those  which 
M.  Malus  discovers;  because,  though  titey  may  not  be  incompatible  with 
those  fads,  they  certainly  give  no  assistance  in  explaining  them.''  1  Even 
Malus  himself  was  at  first  of  opinion  that  the  phenomena  of  polariza- 
tion were  equally  irreconcilable  with  both  the  undulatory  and  mole- 
cular theories;  au  opinion  which  he  distinctlj-  expressed  in  a  letter 2 
to  Young. 

Somewhat  later,  however,  we  find  Young  beginning  to  entertain  a 
more  satisfactory  view  of  the  case,  as  appears  by  the  following  pas- 
sage from  a  letter  addressed  by  him  to  Arago'in  1817:  "  1  have  been 
reflecting  upon  the  possibility  of  giving  an  imperfect  explanation  of  the 
affection  of  light  which  constitutes  polarization,  without  departing 
from  the  genuine  doctrine  of  undulations.  It  is  a  principle  of  this 
theory  that  all  undulations  are  simply  propagated  through  homoge- 
neous mediums  in  concentric  spherical  surfaces,  like  the  undulations 
of  sound,  consisting  simply  of  the  direct  and  retrograde  motions  of 
their  particles  in  the  direction  of  the  radius,  with  their  concomitant 
condensations  and  rarefactions.  Aud  yet  it  is  possible  to  explain  in 
this  theory  a  transverse  vibration,  propagated  also  in  the  direction  of 
the  radius,  and  with  equal  velocity;  the  motions  of  the  particles  bear- 
ing a  certain  constant  direction  with  respect  to  that  radius ;  and  this 
is  polarization."  3 

Now  that  the  idea  of  transverse  vibrations  has  become  familiarized, 
it  seems  to  present  little  difBculty;  yet  it  was  at  first  opposed  to  the 
prepossessions  even  of  the  most  zealous  undulationists.     Fresnellonf 

1  Dean  Peacock's  Life  of  Young,  p.  379. 

2  Works,  vol.  i.  p.  248,  note. 
8  Life,  p.  390. 


REPEATING    GONIOMETER. 


161 


brought  to  perfection  without  at  the  same  time  inducing 
a  corresponding  amelioration  in  the  latter.  In  propor- 
tion as  the  crystal lographic  ideas  of  Haiiy  acquired  more 
exactness,  it  was  found  necessary  to  employ,  for  the  meas- 
urement of  the  angles  of  the  crystals,  methods  of  increas- 
ing precision. 

Wollaston  supplied  this  Avant  by  the  invention  of  the 
reflective  goniometer  which  bears   his  name.*      Malus 

hesitated  fullj-  to  adopt  the  idea,  after  it  had  occuired  to  him  as  the 
only  mode  of  representing  polarization,  on  the  ground  of  being  unable 
to  reconcile  it  with  mechanical  notions;  and  this  more  precisely  as 
to  the  notion  of  transverse  vibrations  alone  being  produced,  which 
constituted  this  theory  in  all  its  simplicity ;  whereas  Young  had  (as 
we  have  just  seen)  believed  both  these  and  longitudinal  \\hrat\ons  to 
coexist.  To  establish  this  point,  he  expressly  says,  was  the  main  dif- 
ficulty which  embarrassed  him.i — Translator. 

*  The  essential  principle  of  the  reflective  goniometer  of  Wollaston 
is  extremely  simple,  and  consists  in  this:  a  piece  of  crystal  or  any 


1  Ann.  de  Chimie,  1831,  torn.  xvii.  p.  184. 


162  MALUS. 

added  to  the  perfection  of  the  English  instrument  by- 
giving  it  the  principle  of  repetition.'^     He  desired  thus  to 

other  object  having  two  plane  surfaces  a  and  J,  capable  of  reflecting 
light,  is  fixed  at  the  centre  of  a  graduated  circle,  to  its  index  i.  It  is 
first  brought  into  such  a  position  that  the  image  of  an  object  x,  by  re- 
flexion from  the  surface  «,  is  seen  by  the  eye  coincident  with  another 
object  Y,  seen  directly;  the  index  marking  0.  It  is  then  turned  round 
till  the  same  thing  is  observed  with  the  surf^ice  &,  when  the  index 
marks/;;  the  arc  op  measures  the  inclination  of  the  two  surfaces  a  b, 
since  the  surface  h  now  occupies  the  same  position  with  respect  to  the 
circle  which  a  did  before. —  Translator. 
*  The  principle  of  '■'■  repetition''''  may  be  thus  briefly  stated.     To  any 


graduated  circular  instrument  intended  for  measuring  the  angular 
distance  of  two  objects  x  y,  there  is  added  an  inner  circle  c,  moving 
about  the  same  centre,  to  which  is  fixed  the  part  t,  which  (by  what- 
ever means)  fixes  the  position  of  the  object;  while  an  index  i  can  be 
either  fixed  to  the  inner  c,  or  to  the  outer  circle  a,  by  clamping,  or 
can  move  independently.  First,  the  index  i  being  clamped  to  c,  then 
pointing  to  0,  while  t  is  directed  to  the  object  x;  the  part  t  is  then 
turned  to  Y,  while  i  moves  over  an  arc  o  1,  equal  to  that  between  x 
and  Y,  and  points  to  1.  Secondly,  i  is  clamped  to  a  at  ],  and  un- 
damped from  c;  <  is  moved  back  on  x;  i  is  undamped  from  a,  and 
clamped  to  c;  and  Amoving  with  i  is  directed  to  y;  i  consequently 
comes  to  2,  passing  over  an  equal  arc.  Thirdly,  the  same  operation  is 
repeated,  and  i  comes  to  3,  and  so  on  for  as  many  times  as  may  be 
desired.     The  arc  read  off  in  each  instance  will,  from  the  errors  of 


ACADEMY   OF    SCIENCES.  163 

be  able  to  compensate  the  errors  of  division  by  successive 
readings  off,  and  to  render  tlie  observer  indejiendent  of 
the  inaccuracies  which  the  artist  might  have  committed 
in  dividing  the  circles.  Unfortunately  natural  crystals, 
on  which  it  is  possible  to  use  with  any  advantage  the 
metliod  of  re[)etition,  are  by  no  means  common.  But 
the  method  preserves  all  its  theoretical  value  when  it  is 
the  object,  in  optical  researches,  to  measure  the  angles  of 
prisms  formed  by  truly  worked  and  perfectly  polished 
planes.  At  the  same  time  it  is  but  just  to  observe  that 
the  idea  of  employing  the  reflexion  of  light  for  the  meas- 
urement of  angles,  is  due  to  the  celebrated  physicist 
Lambert. 

MALUS   A  CANDIDATE   FOR  THE  ACADEMY  OF  SCIENCES. 
SITUATIONS  WHICH  HE  FILLED. HIS  DEATH. 

The  more  than  ordinary  labours  of  Malus,  of  which 
I  have  just  given  a  rapid  analysis,  obtained  for  him  the 
most  sincere  testimonials  of  esteem  and  admiration  from 
men  of  science  of  all  countries.  He  was  named  a  mem- 
ber of  the  Society  of  Arcueil,  wdiich  was  composed  of  a 
small  number  of  men  of  science  assembling  under  the 
auspices  of  Laplace  and  Rerthollet.* 

A  place  in  the  Section  of  Physics  of  the  Listitute  hav- 
ing become  vacant  in  1810  by  the  death  of  Montgolfier, 
Malus  was  naturally  one  of  the  candidates  who  presented 
themselves  to  fill  up  the  place  of  the  illustrious  physicist. 

graduation,  be  diflerent.  As  avij  number  of  repetitions  may  be  taken, 
we  may  have  a  mean  result  accurate  to  any  extent  desired. —  Trans- 
lator. 

*  The  members  of  the  Society  of  Arcueil  were — Laplace,  C.  L.  Ber- 
thollet,  Biot,  Gay-Lussac,  Humboldt,  Tli^nard,  De  Candolle,  Collet- 
Descoutils,  A.  B.  Berthollet,  Malus,  Arago,  Berard,  Chaptal,  Dulong, 
Poisson. 


164  MALTJS. 

Among  the  candidates  there  was  conspicuous  an  en- 
gineer of  roads  and  bridges,  who  had  also  borne  a  part  in 
the  Egyptian  expedition,  and  whose  connections  with  the 
academicians  were  numerous  and  of  old  date.  Every 
one,  therefore,  foresaw  that  the  place  would  be  vigorously 
contested.  On  the  day  of  election,  August  13,  1810,  one 
of  Malus's  friends  undertook  to  bring  him  the  news  of 
the  result  the  moment  it  was  known.  But  by  an  un- 
fortunate combination  of  circumstances  the  scrutiny  was 
not  opened  till  a  later  time  than  usual.  Malus  obtained 
31  votes,  his  opponent  22.  The  friend  of  Malus,  just 
alluded  to,  did  not  lose  a  moment  in  going  to  him  to  an- 
nounce the  happy  result.  But  the  usual  hour  at  which 
the  news  ought  to  have  reached  him  having  long  passed, 
the  great  physicist  believed  himself  to  have  been  defeated, 
and  abandoned  himself,  in  spite  of  all  the  consolations 
which  his  wife  afforded  him,  to  the  deepest  despondency. 
Thus  the  inti-epid  soldier  of  the  army  of  Sambre  and 
Meuse, — he  who  had  seen  the  near  approach  of  death  at 
the  combat  of  Chebreys,  at  the  battle  of  the  Pyramids, 
on  the  day  of  the  revolt  of  Cairo,  in  the  immortal  day  of 
Heliopolis, — the  oificer  who  at  Jaffa  and  Damietta  had 
sustained  the  attacks  of  the  plague  with  such  firmness  of 
mind, — allowed  himself  to  yield  and  sink  under  the  sup- 
posed want  of  success  in  an  election  of  the  Academy  ! 
Let  us  preserve  and  value  these  recollections  !  Who 
will  venture  to  maintain  the  uselessness  of  such  institu- 
tions when  he  sees  the  author  of  one  of  the  greatest  dis- 
coveries of  modern  times  attach  such  a  price  to  the  title 
of  Academician  ?  Who  does  not  perceive  with  what 
emulation  young  experimentalists  ought  to  be  animated, 
when  the  society  in  which  they  aspire  to  take  their  place, 
constantly  anxious  to  repel  from  itself  all  suspicion  of 


ACADEMY    OF    SCIENCES.  165 

party  influence,  holds  itself  in  the  first  position  in  public 
esteem  by  taking  the  greatest  care  always  to  recruit  its 
ranks  solely  from  among  those  who  are  most  worthy. 

Mains  had  become  major,  a  rank  corresponding  with 
that  of  lieutenant-colonel,  December  5,  1810.  The  gov- 
ernment had  often  entrusted  him  with  the  mission  to 
classify  in  their  order  of  merit  the  officers  of  artillery  and 
engineers  at  their  departure  from  the  Practical  School  of 
Metz.  He  became  afterwards  examiner  of  the  pupils  of 
the  Ecole  Polytechnique  for  descriptive  geometry,  and 
the  sciences  dependent  on  it. 

On  the  14tli  Vendemiaire  an  IX.*  Mains  wrote  from 
Benisouf  to  his  friend  Lancret :  "•  I  live  here  like  a  her- 
mit ;  I  pass  whole  days  without  speaking  a  word."  It 
appeared  that  our  friend  often  abandoned  himself  to  his 
taste  for  silence.  The  pupils  of  the  Ecole  Polytechnique 
and  the  Ecole  d'Application,  related  that  in  going  over 
their  exerqises  he  contented  himself  by  pointing  out  with 
his  finger  the  parts  on  which  he  required  explanations, 
without  saying  a  word.  This  mode  of  asking,  which  con- 
trasted so  singularly  with  that  of  some  other  examiners,  his 
contemporaries,  not  a  little  astonished  them.  But  they 
did  not  the  less  do  complete  justice  to  the  enlightened 
patience,  the  intelligence,  and  the  perfect  honesty  which 
characterized  all  the  decisions  made  by  Malus  at  the  close 
of  his  examinations.  Malus  filled,  ad  interim,  in  1811, 
the  functions  of  Director  of  Studies  at  the  Ecole  Poly- 
technique. There  were  only  wanting  some  regimental 
formalities  to  entrust  to  him  definitively  this  important 
employment. 

The  companion  of  his  choice  whom  he  went  to  seek  at 
Giessen  after  the  expedition  to  Egypt,  threw  over  his 
*  October  5, 1800. 


166  MALUS. 

existence  an  unspeakable  happiness.  Tlie  most  cele- 
brated academies  of  Europe  were  envious  to  secure  him 
as  an  associate.  He  was  loved,  honoured,  and  esteemed 
by  all  who  knew  him.  He  might  look  forward  to  fresh 
and  brilliant  discoveries  of  which  his  genius  gave  prom- 
ise. He  possessed,  in  a  word,  after  the  warlike  labours 
of  his  youth,  all  that  could  attach  him  to  life.  It  was  at 
this  juncture  that,  to  the  loss  of  his  connections,  of  his 
friends,  of  the  sciences,  and  the  national  glory,  life  failed 
him. 

A  consumption,  of  Avhich  he  felt  the  first  symptoms 
about  the  middle  of  1811,  made  rapid  and  alarming 
progress,  perhaps  from  some  seeds  of  the  plague  which 
still  lurked  in  his  debilitated  constitution. 

Our  colleague  did  not  believe  himself  fatally  attacked ; 
for  on  the  evening  before  his  death,  he  exacted  from  one 
of  his  friends  a  promise  to  accompany  him  in  the  course 
of  the  week  to  Montmorency,  whither  he  wished  to  retire 
for  a  short  time  to  breathe  the  country  air.  But  I  can 
cite  a  still  more  demonstrative  proof,  if  possible,  of  the 
illusion  under  which  he  laboured  till  the  last.  Returned 
from  Egypt  with  the  full  persuasion  that  consumption  is 
contagious,  and  above  all  that  it  follows  attacks  of  the 
plague,  he  nevertheless  allowed  Madame  Malus,  with  his 
head  reposing  against  hers,  to  watch  his  least  motions,  and 
constantly  to  be  surrounded  with  the  atmosphere  which 
he  had  breathed. 

To  the  last  this  admirable  woman  could  not  believe  in 
the  misfortune  which  threatened  her ;  and  when  the 
illustrious  savant  breathed  his  last,  it  was  needful  almost 
to  use  violence  to  detach  her  from  the  inanimate  body  of 
her  husband.  She  survived  him  only  a  few  months. 
Malus  was  only  thirty-seven  years  of  age  when  the 
Academy  lost  him. 


CHARACTER    AND    MAXIMS    OF    MALUS.  167 

CHARACTER     OF     MALUS. MAXIMS     AND     PRECEPTS. 

SUSCEPTIBILITY    OF     MALUS    ON    QUESTIONS    OF    SCI- 
ENTIFIC   PKIORITT. 

Our  colleague  was  of  a  middle  height  and  size.  In 
spite  of  his  reserved  and  cold  manners,  he  had  a  friendly 
heart.  An  excellent  son,  a  tender  and  irreproachable 
husband,  a  devoted  friend, — he  has  left  behind  him,  in 
the  minds  of  all  who  knew  him,  the  reputation,  so  much 
to  be  envied,  of  a  truly  good  man.  His  conduct,  always 
beyond  reproach  even  in  the  most  difficult  conjunctures, 
was  not  merely  dictated  by  an  instinctive  sense  of  right. 
In  the  leisure  of  his  bivouacs  in  Egypt  he  had  put  down 
on  scattered  papers  the  thoughts  and  maxims  on  which 
he  considered  that  his  conduct  ought  to  be  modelled.  I 
will  here  cite  some  of  them  which  would  not  disgrace,  I 
think,  the  most  celebrated  collections  published  by  any 
of  our  philosophers. 

"  All  the  actions  of  life  ought  to  tend  towards  the  per- 
fection of  the  soul  and  to  social  harmony." 

"  Hope  is  a  source  of  happiness  which  is  not  to  be 
neglected." 

"  I  will  found  my  enjoyments  on  the  affections  of  the 
heart,  the  visions  of  the  imagination,  and  the  spectacle  of 
nature." 

"  We  must  exercise  patience,  as  the  virtue  most  abso- 
lutely necessary  for  happiness  in  our  moral  existence." 

"  Mediocrity  is  a  desirable  condition  of  life,  since  it 
requires  little  expense." 

"  A  great  part  of  life  often  depends  on  circumstances. 
There  are  good  things  of  which  we  must  take  advantage 
as  they  may  occur  ; — as  we  enjoy  the  spring  of  the  year ; 
the  brightness  of  a  fine  day  ;  or  the  odour  of  a  rose." 


168  MALUS. 

"  As  we  cannot  give  children  the  idea  of  good,  we 
ought  to  give  them  the  habit  of  it." 

"  Even  when  we  stifle  reason,  conscience  comes  as  a 
corps  de  reserve  to  oppose  a  barrier  to  irregularity." 

"  I  do  not  like  men  who  weigh  their  own  good  deeds." 

I  find  also  in  the  papers  from  which  the  preceding 
forms  a  very  short  extract,  a  thought  expressed  in  the 
following  terms  : — 

"  One  becomes  the  slave  of  any  man,  if  injustice  on  his 
part  can  offend  and  grieve  us." 

This  last  precept  is  full  of  wisdom  ;  but  did  the  author 
himself  always  strictly  conform  to  it  ?  On  questions  of 
scientific  pi'iority  has  he  not  sometimes,  to  use  his  own 
expression,  become  the  slave  of  his  opponents?  See  and 
judge  for  yourselves. 

Malus  suspected  a  member  of  the  Institute  of  Egypt 
of  having  wished  to  invade  his  rights  on  the  occasion  of 
an  analytical  calculation  being  communicated  to  that 
learned  body.  He  was  so  preoccupied  with  this  idea 
that  in  a  letter  addressed  to  his  colleague  he  omitted  to 
write  before  his  signature,  "  I  am,  with  consideration, 
your  humble  servant."  The  meaning  of  this  suppres- 
sion of  a  customary  form  of  politeness  is  indicated  in 
positive  terms  in  a  letter  which  I  have  before  me  from 
the  oflieer  of  engineers  to  his  friend  Lancret. 

A  great  geometer  conceived  the  idea  of  a  means  of 
reconciling  the  phenomena  of  double  refraction  with  the 
principle  of  "  least  action,"  and  published  on  this  subject 
a  note  which  every  one  may  read  in  our  scientific  jour- 
nals. 

Malus  was  convinced  that  he  had  himself  first  con- 
ceived the  possibility  of  this  investigation,  and  that  he 
had  spoken  of  it  publicly  before  the  publication  of  that 


SUSCEPTIBILITY    OF    MALUS.  169 

note.  He  did  not  content  himself  with  giving  publicity 
to  his  first  ideas  without  making  any  mention  of  the  note 
from  the  pen  of  so  justly  celebrated  a  writer ;  but,  in 
spite  of  his  accustomed  reserve,  he  expressed  himself  on 
this  subject  on  every  occasion  with  a  vehemence  of  which 
he  would  not  have  been  supposed  capable. 

I  will  cite  a  third  example :  An  academician  believed 
he  had  a  right  to  contest  with  Malus  the  priority  in  an 
important  discovery  vvitii  respect  to  polarization.     Malus 
was   then   at  Metz  ;  his   letters   bear  witness,  in  terms 
which  I  know  not  how  to  repeat,  to  his  extreme  irri- 
tation.    It  appeared  to  him  that  the  pretensions  of  his 
opponent  were  not  well  founded  in  fact,  and  also  that 
justice  enjoined  that  he  should  have  been  allowed  reason- 
able time  to  explore  the  first  beds  of  a  mine  the  discovery 
of  which  belonged  incontestably  to  him.     I  ask,  never- 
theless, whether  the  susceptibility  of  Malus  can  be  alto- 
gether blamed  ?    Those  who  defend  with  so  much  reason 
the  rights   of  property  as    the  corner-stone    of  modern 
civilization   cannot  be   astonished   to   see  our  colleague 
attach  himself  with  so  much  ardour  to  the  defence  of 
what  is  the  first  and  most  incontestable  kind  of  property, 
— that  which  consists  in  the  works  of  the  intellect.     Is  it 
moreover   quite    certain,  when    the  illustrious    physicist 
showed  himself  so  sensitive  on  the  subject  of  the  fruits  of 
his  labours  and  his  genius,  that  he  was  not  looking  for- 
ward to  one  of  these  solemn  meetings  where  the  claims 
of  men  of  science  to  the  remembrance  of  mankind  are 
enumerated  and  appreciated  before  an  enlightened  and 
impartial  public, — a  judge  from  whom  there  is  no  ap- 
peal ?     Would  it  then  be  strange  that,  seeing  himself  in 
imagination    before    this    formidable    tribunal,   he    had 
dreamed  of  coming  there  furnished   with   the   greatest 

SEC.    SEB,  8 


170  MALUS. 

possible  number  of  discoveries  uncontested  and  incon- 
testable ?  and  that  under  the  pressure  of  these  preoccu- 
pations he  had  forgotten  for  an  instant  an  abstract 
maxim  of  philosophy  ?  However  this  may  have  been, 
the  integrity  and  perfect  honour  of  Malus  will  never  be 
called  in  question. 

In  the  collection  of  thoughts  from  which  I  have  just 
given  extracts,  I  read  : — 

"  There  are  very  few  men,  who,  when  they  die,  leave 
behind  them  any  traces  of  their  existence." 

I  hazard  little  in  asserting  that  Malus  Avill  be  reck- 
oned among  these  privileged  few.  His  name  will  go 
down  to  the  most  distant  posterity,  coupled  with  one  of 
those  great  discoveries  which,  independently  of  their 
individual  merit,  have  opened  a  vast  career  to  the  inves- 
tigations of  science.  The  immortal  name  of  Malus  will 
remain  ever  inseparable  from  that  of  polarization,  under 
which  all  the  most  curious,  the  most  fertile,  the  most  bril- 
liant phenomena  of  modern  optics  are  grouped. 


FRESNEL. 


PRELIJIINART   NOTICE. 

The  Biography  of  Fresnel,  the  first  which  I  had  to 
read,  as  Perpetual  Secretary,  at  a  public  meeting  of  the 
Academy,  gave  rise  to  incidents  which  several  historians 
of  our  Revolution  of  1830  reported  incorrectly.  I  thus 
feel  myself  bound  to  give  the  true  version  of  the  facts. 
On  arriving  at  the  Academy,  July  the  26th,  1830,  I  read 
in  the  Moniteur  the  famous  ordinances.*  I  understood 
in  an  instant  all  the  political  consequences  which  these 
acts  would  bring  in  their  train  ;  I  considered  them  as  a 
national  misfortune,  and  I  at  once  resolved  to  take  no 
part  in  the  literary  solemnity  for  which  we  had  been  con- 
voked. I  announced  my  resolution  in  these  lines,  which 
were  to  be  substituted  for  the  prepared  eloge : — 

"  Gentlemen, — If  you  have  read  the  Moniteur  your 
thoughts  must  doubtless  be  impressed  with  a  deep  sad- 
ness, and  you  will  not  feel  astonished  that,  for  my  part, 
I  have  not  sufficient  calmness  of  mind  to  be  able  to  take 
part  in  this  ceremony." 

I  committed  the  fault  of  communicating  this  resolution 
to  several  of  my  colleagues.     From  that  moment  difficul- 

*  In  allusion  to  the  abrogation  of  the  Charter  by  the  ministers  of 
Charles  X. 


172  FRESNEL. 

ties  arose  on  all  sides.  "  If  you  execute  your  project," 
they  said  to  me,  "the  Institute  will  be  abolished;  now, 
have  you,  the  youngest  member  of  the  Academy,  any 
right  to  provoke  such  a  catastrophe  ?  "  And  to  support 
this  remark,  they  pointed  out  to  me  several  savants  whose 
sole  livelihood  lay  in  their  appointment  as  members  of 
the  Institute.  These  observations,  strongly  represented, 
shook  my  determination.  The  strife  nevertheless  became 
hotter ;  I  could  consent  to  read  Fresnel's  eloge,  but  I  ob- 
stinately refused  to  cut  out  the  passages  which  just  before 
had  appeared  to  be  irreproachable,  on  the  necessity  to 
comply  with  the  charter  strictly,  if  it  was  not  wished 
to  open  again  the  career  of  revolutions.  Cuvier,  from 
friendship  for  me,  and  also  from  interest  in  the  Academy, 
was  especially  eager  to  obtain  these  suppressions.  I 
communicated  this  circumstance  to  Villemain,  who,  with- 
out perceiving  that  the  great  naturalist  was  within  hear- 
ing, exclaimed  :  "  That  is  signal  cowardice."  From 
thence  quarrels  and  personalities  arose,  of  which  I  should 
feel  scruples  in  depositing  the  remembrance  here.  The 
result,  at  the  time  of  this  lamentable  circumstance,  Avas, 
that  the  passages  in  question  were  preserved  in  the  read- 
ing, and  became  the  object,  on  the  part  of  the  public,  of 
enthusiastic  applause,  which  did  not  appear  to  be  merited 
either  by  the  matter  or  the  form.  I  must  own  that  I  was 
much  surprised  when,  on  coming  out  of  the  meeting,  the 
Duke  of  Ragusa  whispered  to  me,  "  God  grant  that  I 
may  not  have  to  go  to-mori'ow  to  seek  for  you  at  Vin- 
cennes." 


introductory  remarks.  173 

This  Biography  was  read  at  the  Public  Meeting  of 
THE  Academy  of  Sciences  on  the  26th  of  July, 
1830. 

Gentlemen, — "There  are  men  who  may  be  succeeded, 
but  whom  no  one  can  replace."     These  words  of  one  of 
the  most  honoured  writers  of  our  time,  so  often  reproduced 
as  the  conventional  formula  on  occasions  like  the  present, 
are  to-day  in  my  mouth  the  faithful  expression  of  what  I 
feel.     How  could  I,  indeed,  without  the  deepest  emotion, 
now  occupy  before  this  tribunal  a  place  which  has  been 
so  worthily  filled,  during  eight  years,  by  the  illustrious 
geometer  whose  unexpected  death  has  been  a  source  of 
no  less  regret  to  friendship,  than  to  science  and  to  letters. 
It  is  not  here.  Gentlemen,  for  the  first  time  that  this 
sincere  avowal  of  my  well-founded  diffidence  has  been 
heard.     Nearly  all  the  members  of  the  Academy  have  in 
turn  been  the  confidants  of  my  scruples,  and  their  encour- 
aging kindness  had  scarcely  succeeded  in   surmounting 
them.     Devoted  for  a  long  time  past  to  purely  scientific 
researches,  entirely  destitute  of  the  literary  claims,  Avhich 
up  to  this  moment  had  appeared  indispensable  in  the  dif- 
ficult functions  which  were  confided  to  me,  I  could  only 
possess  in  the  eyes  of  the  Academy  the  slight  merit  of 
continued  zeal,  of  unlimited  devotion  to  its  interests,  of 
an  ardent  desire  manifested  on  all  occasions  to  see  the 
renown  which  it  had  acquired  enlarge,  if  that  were  pos- 
sible, and  extend  itself  in  all  quarters.     The  void  which 
M.   Fourier  has  left  among  us    (as  I  was  the  first  to 
acknowledge,  and  I  acknowledged  it  without  reserve)  will 
be  especially  felt  in  these  solemn  meetings  ;  it  is  then 
that  you  will  recall  to  mind  that  language  in  which  the 
most  rigorous  precision  was  so  happily  allied  with  ele- 


174  FRESNEL. 

gance  and  with  grace.  Also  I  could  not  but  persuade 
myself  that  the  indulgence  of  the  Academy  presaged  in 
some  degree  that  with  which  the  public  would  deign  to 
honour  me  ;  otherwise  could  I  have  dared  to  make  an 
inexperienced  voice  heard  here,  after  the  eloquent  inter- 
preter whom  we  have  just  lost,  and  by  the  side  of  him 
whom  we  have  the  happiness  still  to  possess  ? 

I  hasten,  moreover,  to  explain  that  this  eloge  departs 
fi'om  the  ordinary  form.  I  shall  even  ask  the  favour  of  its 
being  looked  upon  as  simply  a  scientific  memoir,  in  which, 
taking  occasion  from  the  labours  of  our  late  associate,  I 
have  the  opportunity  of  examining  the  progress  which 
has  been  made  in  our  times  in  several  of  the  most  impor- 
tant branches  of  optics.  At  an  epoch  when  the  courses 
of  lectures  at  the  College  de  France,  of  the  Facvlte  de 
Paris,  of  the  Jardin  du  Roi  are  attracting  so  great  a 
concourse  of  auditors,  it  has  occurred  to  me  that  the 
Academy  of  Sciences  might  directly  address  itself  to  the 
public  (that  friend  of  our  studies,  showing  its  good  will 
by  so  numerous  an  attendance  at  our  meetings)  on  some 
of  the  various  questions  with  which  we  are  specially  occu- 
pied. At  the  same  time  this  is  but  a  simple  attempt  of 
my  own  on  which  I  should  wish  to  be  enlightened ;  the 
critic  will  find  me  docile.  I  hope,  however,  that  the  satis- 
faction of  becoming  initiated  in  a  few  minutes  into  the 
most  curious  discoveries  of  one  century,  may  appear  a 
sufficient  compensation  for  the  inevitable  tediousness 
which  so  many  minute  details  must  cause. 

For  my  own  part,  the  indulgence  on  which  I  count 
will  not  prevent  my  making  every  effort  to  render  myself 
clear.  Fontenelle,  on  a  similar  occasion,  asked  of  his 
auditory  (I  quote  his  own  expression)  "  the  same  atten- 
tion which  they  would  necessarily  give  to  the  romance  of 


BIRTH    AND    EDUCATION.  175 

the  Pi'incess  of  Cleves  if  they  wished  closely  to  follow  the 
plot,  and  to  know  the  whole  beauty  of  it."  I  am  aware 
that  I  should  not  be  right  in  demanding  so  little  ;  but,  on 
the  other  hand,  I  have  the  advantage  of  speaking  before 
an  assembly  familiarized  with  deep  study,  and  from 
which  one  may  confidently  claim  a  degree  of  attention 
which  Fontenelle  himself,  at  the  commencement  of  the 
eighteenth  century,  would  have  found  it  difficult  to  gain 
from  the  frivolous  assembly  he  was  addressing. 

INFANCY  OF  FRESNEL. HIS  ENTRANCE  INTO  THE  POLY- 
TECHNIC  SCHOOL    AND    INTO   THE  CORPS  OF  BRIDGES 

AND  HIGHWAYS. HIS  DEPOSITION  FOR  HAVING  GONE 

TO  JOIN  THE  ROYAL  ARMY  AT  PALUD. 

Augustine  John  Fresnel  was  born  the  10th  of  May, 
1788,  at  Broglie,  near  Bernay,  in  that  part  of  the  ancient 
province  of  Normandy  which  now  forms  the  department 
of  Eure.  His  father  was  an  architect,  and  in  this  quality 
had  been  entrusted  by  the  military  engineer  with  the 
construction  of  the  Fort  of  Querqueville,  at  one  of  the 
extremities  of  the  harbour  of  Cherbourg  ;  but  the  revo- 
lutionary storm  having  forced  him  to  abandon  this  work, 
he  retired  with  all  his  family  to  a  moderate  property 
which  he  owned  near  Caen,  at  Matthieu,  a  little  village 
which  already  was  not  without  some  notoriety,  being  the 
birthplace  of  the  poet  John  Marot,  father  of  the  cele- 
brated Clement.  Madame  Fresnel,  whose  family  name 
(Merimee)  was  also  to  become  one  day  dear  to  literature 
and  the  arts,  was  endowed  with  the  most  happy  qualities 
of  heart  and  mind ;  the  solid  and  varied  instruction  which 
she  had  received  in  her  youth  enabled  her  to  assist  ac- 
tively, during  eight  consecutive  years,  in  the  efforts  which 


176  FRESNEL, 

her  husband  made  for  the  education  of  their  four  children. 
The  progress  of  the  eldest  son  was  brilliant  and  rapid. 
Augustine,  on  the  contrary  advanced  extremely  slowly  in 
his  studies  ;  at  eight  years  of  age  he  could  scarcely  read. 
This  want  of  success  might  be  attributable  to  the  very 
delicate  condition  of  the  young  scholar,  and  to  the  pre- 
cautions which  it  rendered  necessary;  but  it  will  be  still 
better  understood  when  it  is  known  that  Fresnel  never 
had  any  taste  for  the  study  of  languages  ;  that  he  always 
set  very  little  value  on  the  exercises  which  address  them- 
selves solely  to  the  memory  ;  that  his  own,  which  was 
moreover  very  rebellious  generally,  refused  almost  ab- 
solutely to  retain  words  from  the  moment  that  they 
were  detached  from  a  clear  argument  and  displaced  in 
arrangement:  I  must  also  own,  witliout  hesitation,  that 
those  whose  predictions  concerning  the  future  of  a  child 
are  founded  on  the  precise  estimate  of  the  first  places 
which  he  obtained  at  the  college,  in  theme  or  in  transla- 
tion, would  never  have  imagined  that  Augustine  Fresnel 
would  become  one  of  the  most  distinguished  savants  of 
our  epoch.  As  to  his  young  comrades,  they  had,  on  the 
contrary,  judged  with  that  sagacity  which  rarely  deceives 
them  ;  they  called  him  "  the  genius."  This  pompous  title 
was  unanimously  accorded  him  on  account  of  the  experi- 
mental researches  (I  may  be  allowed  this  expression,  it  is 
but  just)  to  which  he  devoted  himself  at  the  age  of  nine 
years,  whether  for  determining  the  relative  length  and 
bore  which  give  the  greatest  power  to  the  little  elder- 
wood  popguns  which  children  use  in  their  play,  or  in  de- 
termining which  are  the  wood-,  dry  or  green,  which  are 
best  to  use  in  making  bows,  under  the  double  considera- 
tion of  elasticity  and  strength.  The  physicist  of  nine 
years  old  had,  indeed,  executed  this  little  work  with  so 


POLYTECHNIC    SCHOOL.  177 

much  success,  that  the  toys,  hitherto  very  inoffensive,  had 
become  dangerous  arms,  which  he  had  the  honour  of"  see- 
ing proscribed  by  an  express  resolution  of  the  assembled 
parents  of  all  the  combatants. 

In  1801,  Fresnel,  aged  thirteen,  quitted  the  paternal 
hearth,  and  went  to  Caen  with  his  elder  brother.  The 
central  school  of  this  town,  where  the  instruction  has 
always  been  creditable,  presented  then  a  reunion  of  pro- 
fessoi's  of  the  rarest  merit.  The  excellent  lessons  ia 
mathematics  from  M.  Quenot,  the  course  of  general  gram- 
mar and  logic  from  the  Abbe  de  la  Riviere,  eminently 
contributed  to  develop  in  the  young  pupil  that  sagacity, 
that  rectitude  of  mind,  which  guided  him  afterwards  so 
happily  in  the  apparently  inextricable  labyrinth  of  natural 
phenomena  which  he  succeeded  in  clearing.  The  com- 
munication of  knowledge  is,  of  all  the  benefits  which  we 
receive  in  our  youth,  that  of  which  a  generous  heart  pre- 
serves the  deepest  remembrance.  Hence  the  gratitude 
which  Fresnel  had  felt  towards  his  worthy  professors  at 
Caen  was  always  lively  and  respectful.  The  central 
schools  themselves  always  occupied  a  large  share  of  his 
recollections  ;  and  I  have  some  reason  to  believe  that 
many  reminiscences  of  these  ancient  institutions  would 
have  been  found  in  a  plan  of  study  which  he  wished  to 
publish. 

Fresnel  entered  the  Polytechnic  School  at  the  age  of 
sixteen  and  a  half,  where  his  eldest  brother  had  preceded 
him  one  year  before.  His  health  was  at  that  time  ex- 
tremely weak,  and  gave  reason  to  fear  that  he  would  be 
unable  to  support  the  fatigue  of  so  I'ough  a  noviciate  ; 
but  that  feeble  body  enclosed  the  most  vigorous  soul,  and 
in  all  things  the  firm  will  to  succeed  is  already  half  the 
success ;     moreover,   the    dextex-ity   of   Fresnel   in   the 


178  FRESNEL. 

graphic  arts  was  nearly  unequalled,  and  on  this  ground 
he  could  fully  compete  with  the  cleverest  of  his  com- 
rades, even  whilst  imposing  upon  him  far  less  work  in  a 
day.  Wiien  Fresnel  went  through  the  course  at  the 
Polytechnic  School,  a  savant,  Avhose  zeal  age  has  not 
cooled, — whom  the  Academy  of  Sciences  has  the  happi- 
ness to  number  amongst  its  most  active  and  most  assidu- 
ous members,  and  whom,  as  he  is  listening  to  me,  I  will 
only  designate  by  the  simple  title  of  the  chief  of  living 
geometers, — fulfilled  the  duties  of  examiner.  In  the 
course  of  the  year  1804,  he  proposed  to  the  pupils,  as  a 
subject  of  competition,  a  geometrical  question.  Several 
solved  it ;  but  the  solution  of  Fresnel  particularly  struck 
the  attention  of  our  colleague  ;  for  superior  men  enjoy 
the  happy  privilege  of  discovering,  even  from  slight 
indications,  the  talents  which  will  shine  brightly.  M. 
Legendre  (his  name  escapes  from  my  lips)  complimented 
the  young  prize-man  publicly.  Proofs  of  encourage- 
ment coming  from  so  high  a  quarter  revealed  to  Fresnel, 
perhaps  for  the  first  time,  the  secret  of  his  own  merit, 
and  conquered  an  excessive  feeling  of  mistrust,  which 
with  him  produced  the  most  vexatious  results,  because  it 
prevented  him  from  attempting  new  paths. 

On  leaving  the  Polytechnic  School,  Fresnel  passed 
into  the  department  of  the  "  ponts  et  chaussees."  When 
he  had  obtained  the  rank  of  ingenieur  ordinaire,  he  was 
sent  into  the  department  of  the  Vendee,  where  the  gov- 
ernment, desirous  to  efface  the  traces  of  our  deplorable 
civil  discord,  raised  up  all  that  war  had  thrown  down, 
opened  communications  destined  to  give  life  to  the 
country,  and  laid  the  foundations  of  a  new  town.  Every 
pupil,  whatever  may  be  the  career  he  is  about  to  enter 
upon,  awaits  with  the  most  eager  impatience  the  instant 


BECOMES    AN    ENGINEER, 


179 


at  which  he  may  give  up  that  title.  To  him,  in  four- 
and-twenty  hours,  the  appearance  of  the  world  becomes 
completely  changed  ;  he  has  hitherto  received  instruc- 
tion ;  he  is  going  to  create  it.  His  future  seems,  more- 
over, to  promise  him  all  that  a  century  may  have  offered 
in  the  way  of  brilliant  occurrences  to  some  few  individ- 
uals favoured  by  fate. 

Few  engineers,  for  example,  receive   their  diplomas 
without  believing  themselves  from   this  moment  called 
(like  new  "  Riquets ")   either  to  join  the  ocean  to  the 
Mediterranean  by  a  great  canal  which  will  carry  mer- 
chantmen even   to  the  centre  of  a  kingdom,  or  to  trace 
on  the    slope   of  the  Alps  the  winding  and  bold  road 
whose  summit  is  lost  amidst  eternal  snow,  but  which  the 
traveller  nevertheless   will  face    even   in    the  depth  of 
winter.     One  has   conceived  the  hope   of  ornamenting 
the  capital  with  one  of  those  light,  and  at  the  same  time 
steady  bridges,  where  the  bold  chisel  of  a  David  may 
some  day  come  to  animate  the  marble  ;  another,  remod- 
elling the  gigantic  works  of  Cherbourg,  arrests  tempests 
at  the   entrance  of  roadsteads,  provides  useful  harbours 
for   merchantmen,   associates   himself   finally   with   the 
glory  of  the  national  squadrons  by  furnishing  them  with 
ncAv  means  of  attack  and  defence.     The  less  ambitious 
have   dreamt  of  improving  the   course  of  the  principal 
rivers,  and  rendering  their  waters  deeper  and  less  rapid 
by  means  of  embanknaents  ;  of  checking  those  moving 
mountains  which,  under  the  name  of  sandhills,  gradually 
invade  rich  countries  and   transform   them  into  sterile 
deserts. 

I  will  not  venture  to  affirm  that,  notwithstanding  the 
extreme  moderation  of  his  desires,  Fresnel  entirely 
escaped  these  happy  dreams  of  youth.    At  all  events  the 


180  FRESNEL. 

sequel  was  unexpected.  To  level  small  portions  of 
road  ;  to  seek,  in  the  countries  placed  under  his  superin- 
tendence, for  beds  of  flint;  to  preside  over  the  extraction 
of  the  materials ;  to  see  to  their  deposition  on  the  road, 
or  in  the  wheel  ruts ;  to  execute,  here  and  there,  a 
bridge  over  the  irrigation  drains  ;  to  reestablish  some 
metres  of  bank  which  the  torrent  has  carried  away  in  its 
progress ;  to  exercise  principally  an  active  surveillance 
over  the  contractors ;  to  verify  their  accounts  ;  to  esti- 
mate scrupulously  their  woi'ks, — such  were  the  duties, 
very  useful,  though  not  very  lofty,  not  very  scientific, 
which  Fresnel  had  to  fulfil  during  from  eight  to  nine 
years  in  Vendee,  in  Drome,  and  in  Ille  et  Vilaine. 
How  heavily  must  a  mind  of  such  power  have  been 
affected,  when  he  compared  the  use  which  he  might 
have  made  of  those  hours  which  pass  away  so  quickly, 
with  the  way  in  which  they  were  being  spent !  But 
with  Fresnel  conscientiousness  was  always  the  foremost 
part  of  his  character,  and  he  constantly  performed  his 
duties  as  an  engineer  with  the  most  rigorous  scrupulous- 
ness. The  mission  to  defend  the  revenues  of  the  state, 
to  obtain  for  them  the  best  employment  possible,  ap- 
peared to  his  eyes  in  the  light  of  a  question  of  honour. 
The  functionary,  whatever  might  be  his  rank,  who  sub- 
mitted to  him  an  ambiguous  account,  became  at  once  the 
object  of  his  profound  contempt.  Fresnel  could  not 
comprehend  the  conduct  to  which  persons,  in  other 
respects  very  estimable,  believe  themselves  bound  some- 
times by  an  esprit  de  corps.  All  fraternity  ceased  for 
him,  notwithstanding  the  similarity  of  title  and  uniform, 
as  soon  as  any  one  lost  a  probity  free  of  suspicion. 
Under  such  circumstances  the  habitual  gentleness  of  his 
manners   disappeared,  and  gave  place  to  a  sternness,  I 


THE  CAUSE  OF  THE  BOURBONS.        181 

will  even  say  a  roughness,  which  in  this  age  of  conces- 
sions drew  upon  him  numerous  vexations. 

The  purely  speculative  opinions  of  a  studious  man 
concerning  the  political  organization  of  society,  must 
generally  be  of  too  little  interest  to  the  public  to  render 
their  mention  necessary  ;  but  the  influence  which  they 
exercised  on  the  career  of  Fresnel  will  not  allow  me  to 
be  silent  upon  them. 

Fi'esnel,  like  so  many  good  men,  associated  himself 
deeply  in  1814  with  the  hopes  to  which  the  return  of 
the  Bourbon  family  gave  rise.  The  charter  of  1814, 
executed  without  retrospective  effect,  appeared  to  him  to 
contain  all  the  germs  of  a  wise  liberty.  He  saw  in  it 
the  aui'ora  of  a  political  regeneration  which  would,  with- 
out a  check,  extend  itself  from  France  over  all  Europe. 
His  patriotic  spirit  was  excited  with  the  idea  that  our 
beautiful  country  was  about  to  exercise  such  a  pacific 
influence  over  the  good  of  nations.  If,  during  the  Im- 
perial dynasty,  the  great  events  of  Austerlitz,  of  Jena,  of 
Friedland,  had  not  strongly  excited  his  imagination,  it 
was  solely  because  they  appeared  to  him  destined  to  per- 
petuate that  despotism  under  which  France  at  that  time 
bent.  The  disembarkment  at  Cannes,  in  1815,  appeared 
to  him  an  attack  on  civilization ;  and  thus,  without  being 
hindered  by  the  disordered  state  of  his  health,  he  was 
anxious  to  go  and  join  one  of  the  detachments  of  the 
royal  army  of  the  south.  Fresnel  flattered  himself  with 
the  hope  of  meeting  only  with  men  of  his  own  disposi- 
tion, if  I  may  judge  from  the  painful  impression  which 
he  experienced  at  his  first  interview  with  the  general 
under  whose  orders  he  went  to  place  himself.  Touched 
by  the  invalid  appearance  of  the  new  soldier,  the  general 
testified  his  surprise  that  in  such  a  condition  he  should 


182  FRESNEL. 

expose  himself  to  the  fatigues  and  dangers  of  a  civil  war. 
"  Your  superiors,  Sir,"  said  he,  "  have  enjoined  on  you 
this  expedition."  "No,  general,"  he  replied,  "I  have 
taken  no  advice  but  my  own."  "  I  pray  you  tell  me 
without  reserve,  has  any  one  threatened  you  with  not 
paying  your  appointments  ?  "  "  No  such  threat  has  been 
made ;  my  appointments  have  been  regularly  paid." 
"  Very  well ;  I  ought,  between  ourselves,  to  warn  you 
that  you  can  here  reckon  only  on  what  may  be  got  by 
chance."  "  I  have  reckoned  my  own  resources  ;  I 
neither  hope  nor  desire  any  other  recompense.  I  pre- 
sent myself  to  you  to  fulfil  my  duty."  "  I  admire  you, 
Sir  ;  it  is  thus  that  every  good  servant  of  the  royal  cause 
ought  to  think  and  act ;  I  participate  in  your  honourable 
sentiments  ;  you  may  reckon  on  my  good  will." 

That  good  will,  in  fact,  did  not  fail ;  and  the  questions 
which  at  first  had  been  painful  to  Fresnel,  showed  solely 
that  his  questioner,  less  a  novice  in  the  ways  of  the 
world,  knew  by  experience  that  a  popular  gathering, 
under  whatever  colour  it  may  show  itself,  includes  more 
than  a  few  individuals  who  under  high  pretensions  con- 
ceal personal  interests. 

Fresnel  returned  to  Nyons,  his  usual  residence,  almost 
dying.  The  news  of  the  events  of  the  Palud  had  pre- 
ceded him.  The  populace  (we  know  what  this  term  sig- 
nifies in  the  south)  offered  him  a  thousand  insults.  A 
few  days  afterwards  an  imperial  commissary  declared 
his  deprivation  of  his  office,  and  placed  him  under  the 
surveillance  of  the  police.  Far  be  it  from  me  to  ex- 
tenuate the  odious  nature  of  such  a  transaction.  I  ought, 
however,  to  say  that  it  was  executed  without  need- 
less rigour,  and  that  Fresnel  obtained  permission  to  go  to 
Paris;  that  he  lived  there  without  being  disturbed;   that 


FIRST    SCIENTIFIC    PAPERS.  183 

he  was  able  to  renew  his  acquaintance  with  his  old 
fellow  students,  and  to  prepare  for  those  scientific  re- 
searches which  he  designed  to  pursue  in  the  retreat 
where  his  younger  years  had  been  passed.  At  this  time 
Fresnel  had  but  a  very  confused  idea  of  the  brilliant  dis- 
coveries, which,  in  the  early  years  of  the  present  cen- 
tury, entirely  changed  the  aspect  of  optical  science. 

fresnel's  first  scientific  papers. 

The  first  memoir  on  science  which  Fresnel  drew  up, 
dates  from  this  same  year,  1814.  It  was  an  essay  whose 
object  was  to  rectify  the  explanation,  considered  as 
imperfect,  of  the  phenomenon  of  the  aberration  of  the 
light  of  the  stars  hitherto  generally  followed  in  elemen- 
tary works.  Both  geometry  and  physical  science  equally 
bore  out  this  new  administration  ;  but,  unfortunately,  it 
too  closely  resembled  that  already  given  by  Bradley  him- 
self and  by  Clairault.  I  say  unfortunately,  because,  if 
we  should  suppose  that  such  coincidences  are  pleasing  to 
the  self-love  of  a  dehutant,  or  stimulate  his  zeal,  it  would 
be  a  mistake.  On  the  other  hand,  an  author  may  sup- 
port with  philosophy,  I  admit,  the  unpleasant  fact  of 
having  uselessly  employed  his  powers  for  years  in  the 
search  after  a  truth  already  long  since  established  ;  he 
may  give  up,  with  the  best  grace,  the  flattering  hope  of 
seeing  his  name  associated  with  some  brilliant  discovery  ; 
but  might  he  not  feel  much  more  disquieted  when  there 
was  ground  to  fear,  that  from  mere  ignorance  of  the 
existence  of  prior  researches,  of  which  no  one  dreamed, 
he  might  stand  charged  with  plagiarism  ?  when  he  might 
apprehend  that  an  irreproachable  character  was  no  safe- 
guard against  such  imputations  ?  The  public,  notwith- 
standing the  most  express  denials,  will  always   believe 


184  FRESNEL. 

that  an  author  knows  all  that  he  might  be  supposed  to 
know ;  and  the  right  with  which  it  is  invested,  to  ti-eat 
with  implacable  severity  those  vVho  knowingly  borrow 
from  the  labours  of  their  predecessors,  is  the  origin  of 
more  than  one  act  of  injustice.  Thus,  Lagrange  has 
recounted  that  in  his  youth  he  experienced  just  such  a 
profound  mortification,  on  finding,  by  accident,  in  the 
works  of  Leibnitz,  an  analytical  formula  which  he  had 
completely  forgotten,  and  of  which  he  had  spoken  to  the 
Academy  of  Turin  as  a  discovery  of  his  own.  From 
that  day  he  had  nearly  renounced  altogether  the  study 
of  mathematics.  The  demonstration  of  aberration  was 
a  matter  of  too  little  importance  to  inspire  Fresnel  with 
a  similar  discouragement ;  and  besides,  he  had  not  print- 
ed it ;  but  this  circumstance  rendered  him  extremely 
timid ;  and  subsequently  he  never  published  any  memoir 
without  assuring  himself  by  the  testimony  of  some  of  his 
friends,  to  whom  the  academical  collections  were  more 
familiar,  that  he  had  not.  according  to  a  popular  proverb 
which  he  habitually  adopted,  "broken  through  open 
doors."  * 

*  It  is  much  to  be  regretted  that  this  early  production  of  Fresnel 
should  not  have  been  preserved — more  especially  when  we  recollect 
that  the  theoretical  explanation  of  the  aberration  of  light,  though  ap- 
parently well  given  by  Clairault  and  others,  was  for  a  long  time  by 
no  means  clearly  apprehended,  and  far  from  being  exempt  from  all 
necessity  for  further  elucidation.  In  proof  of  this  it  may  suffice  to 
allude  to  the  fact  that,  on  the  occasion  of  the  transit  of  Venus  in 
1769,  two  eminent  astronomers,  Bliss  and  Hornsby,  calculated  the 
efFect  of  aberration  as  accelerating  the  phases  of  the  transit,  while 
Professor  Winthrop,  of  Cambridge,  U.  S.,  argued  that  it  ought  to  be 
that  o^  retarding  them.  Other  discrepancies  of  opinion  in  past  times 
might  also  be  cited;  but  the  most  striking  fact  has  been  the  contro- 
versy in  which  the  whole  subject  has  been  involved'  in  our  times, 
arising  out  of  the  somewhat  startling  ideas  proposed  by  Professor 
Challis.  and  so  largely  discussed  by  that  eminent  mathematician  and 


FIRST    EXPERIMENTAL    RESEARCHE?.  185 

The  first  experimental  researches  of  Fresnel  do  not 
date  earlier  than  the  beginning  of  1815  ;  but  setting  out 
from  this  epoch,  memoirs  succeeded  to  memoirs,  discov- 
eries to  discoveries,  with  a  rapidity  of  which  the  history 
of  science  offers  few  examples.    On  the  28th  of  December, 
1814,  Fresnel  wrote  from  Nyons,  "  I  do  not  know  what 
is  meant  by  the  polarization  of  light ;  beg  my  uncle,  M. 
A.  Merimee,  to  send  me  the  best  works  from  which  I 
may  obtain  information  on  this  subject."     Eight  months 
had   scarcely   elapsed,   when    highly   skilful    researches 
placed  him  among  the  most  celebrated  physicists  of  our 
era.     In  1819  he  carried  off  the  prize  proposed  by  the 
Academy  on    the    difficult    question    of   diffraction.     In 
1823   he  became  a  member  of  that  body  by  an  una- 
nimity of  suffrages, — a  kind  of  success  extremely  rare', 
since  it  implies  not  only  merit  of  the  highest  order,  but 
also,  on  the  part  of  all  the  competitors,  a  frank  and  ex- 
plicit avowal  of  inferiority.     In  1825  the  Royal  Society 
of  London  admitted  him  a  foreign  associate  ;  and,  lastly, 
two  years  later,   the   same  body  adjudged    to  him   the 
Rumford   Medal.     This   homage  from  one  of  the  most 
illustrious   scientific  bodies   in   Europe, — this   judgment, 
pronounced  among  a  rival  people,  by  the  countrymen  of 
Newton,  in  favour  of  an  experimenter  who  attached  little 
value  to  his  discoveries,  except  as  subverting  a  system  of 
which  that  great  genius  was  the  defender, — appears  to 
me  to  possess  all  the  characters  of  a  decree  which  pos- 
terity will  confirm.     I  hope,  then,  it  will  be  permitted 
me  to  appeal  to  this  decree,  if  in  spite  of  all  my  desire 

Professor  Stokes.  (See  Pkilos.  Mag.  1845-6.)  We  merely  allude 
to  these  points  in  order  to  show  how  interesting  it  would  have  been 
to  have  become  acquainted  with  the  view  taken  of  such  a  subject  by 
a  mind  so  eminently  anticipative  as  that  of  Fresnel. —  Translator. 


186 


FRESNEL. 


to  confine  myself  to  the  strict  boundaries  of  truth,  and 
the  consciousness  which  I  have  of  never  having  trans- 
gressed them,  it  should  happen  that  this  eloge  should  be 
accused  of  some  exaggeration.  Though  I  must  avow  it 
would  be  a  reproach  for  which  I  should  feel  little  as  the 
friend  of  Fresnel,  if  it  were  incumbent  on  me  to  repel 
it,  it  would  be  solely  in  the  capacity  of  the  organ  of  the 
Academy  :  the  office  which  I  this  day  fill,  in  the  name 
of  my  colleagues,  ought  to  be  marked  by  a  precision 
and  severity  as  great  as  that  of  the  exact  sciences  with 
which  it  is  concerned. 

REFRACTION'. 

The  labours  of  Fresnel  almost  exclusively  relate  to 
optics.  In  order  to  avoid  tedious  repetitions,  I  shall 
classify  them,  without  regard  to  the  order  of  dates,  in 
such  a  way  as  to  collect  in  a  single  group  all  those  which 
relate  to  analogous  subjects.  The  first  which  will  engage 
my  attention  are  the  phenomena  of  refraction. 

A  straight  rod  partly  immersed  in  water  appears  bent 
or  broken  ;  the  rays  by  which  we  see  the  part  immersed 
must,  therefore,  have  changed  their  route  or  have  been 
broken  themselves,  in  passing  out  of  the  water  into  the 
air.  It  was  till  lately  supposed  that  to  this  one  observa- 
tion we  were  to  restrict  the  entire  knowledge  of  the  an- 
cients on  the  subject  of  refraction.  But  in  exhuming 
from  the  dust  of  libraries,  where  so  many  treasures  are 
yet  concealed,  a  manuscript  of  the  optics  of  Ptolemy,  it 
has  been  found  that  the  School  of  Alexandria  had  not 
confined  itself  to  establishing  the  mere  fact  of  refraction ; 
for  this  work  includes  from  all  incidences,  numerical  de- 
terminations, tolerably  exact,  of  the  deviations  of  the 
rays,   whether  they  pass  out  of  air  into  water  or  into 


LAW    OF    REFRACTION.  187 

glass,  or  whether  they  enter  glass  on  passing  out  of 
water.  As  to  the  mathematical  law  of  these  deviations, 
which  the  Arabian  Alhasen,  the  Pole  Vitellio,  Kepler, 
and  other  physicists  had  sought  in  vain,  it  is  to  Descartes 
that  we  owe  its  announcement :  I  say  Descartes,  and 
Descartes  *  alone  ;  for  if  the  later  claims  put  forth  by 

*  In  thus  strongly  claiming  for  Descartes  the  discovery  of  the  law 
of  refraction  which  English  writers  ascribe  to  Willebrod  Snell,  Arago 
might  be  supposed  actuated  by  a  feeling  of  national  pride,  which  not, 
unfrequently,  perhaps,  influenced  him  on  questions  of  this  kind.  The 
strong  expression  with  which  he  concludes  the  sentence,  seems,  how- 
ever, to  point  to  a  more  philosophical  motive,  and  to  refer  the  claim 
of  Descartes  to  considerations  derived  from  the  connection  of  the  law 
of  refraction  with  his  theories.  However  this  may  be,  it  may  be  well 
briefly  to  recapitulate  the  facts  of  the  case.  The  ancients,  especially 
Ptolemy,  had  amassed  many  measured  results.  Alhasen  (a.d.  1100) 
stated  the  general  principle  that  refraction  in  a  denser  medium  causes 
the  ray  to  deviate  nearer  to  the  perpendicular.  Vitellio  collected  a 
number  of  measured  results  in  different  media  at  different  angles  of 
incidence;  among  which  Kepler  attempted,  with  his  usual  ardour,  to 
endeavour  to  deduce  some  general  numerical  relation.  He,  however, 
could  proceed  no  further  than  this — that  while  the  an(ile  of  incidence 
is  but  small,  it  is  in  a  constant  ratio  (dependent  on  the  nature  of  the 
medium;  to  that  of  refraction ;  but  that,  as  we  deviate  more  from  the 
perpendicular,  the  rule  becomes  less  accurate,  and  soon  fails. 

Willebrod  Snell,  in  1621,  investigated  and  established,  by  com- 
parison of  numerical  results,  a  general  geometrical  mode  of  repre- 
senting the  case,  which,  expressed  in  modern  terms,  is  the  true  law  of 
refraction  (or  sin  i=fJ-  sin  »•),  a  constant  ratio  between  the  sines,  not 
the  angles,  where  i  and  r  are  the  angles  of  incidence  and  refraction, 
and  /J,  the  constant  or  refractive  index.  And  the  relation  observed 
by  Kepler,  which  is  true  so  long  as  the  angle  is  small  enough  to  be 
nearly  proportional  in  its  sine,  is  thus  extended  and  generalized. 
Snell  died  in  1626  without  having  printed  his  discovery;  but  it  had 
been  shown  in  MS.  to  many  persons,  especially  to  Huyghens,  who 
fully  perceived  its  value  and  importance.  And  it  is  on  his  authority 
that  the  discovery  was  properly  assigned  to  Snell  by  Montucia, 
Bossut,  and  other  writers.  Huyghens,  however,  did  not  publish  any 
account  of  the  matter  till  it  appeared  in  his  Dioptricu,  which  was 
printed  after  his  death  in  1700. 


188 


FRESNEL. 


Huyghens  in  favour  of  his  fellow  countryman  Snell  be 
accepted,  we  must  give  up  the  pretence  of  writing  the 
history  of  science. 

A  mathematical  law  has  more  importance  than  an 
ordinary  discovery,  for  it  is  itself  a  source  of  discoveries. 
From  it  simple  analytical  transformations  point  out  to 
observers  a  multitude  of  results  more  or  less  hidden,  of 
which  they  would  with  difficulty  have  become  aware  ; 
but  such  results  cannot  be  accepted  without  reservation, 
so  long  as  the  truth  of  the  primary  law  rests  solely  on 
measurements.  It  is  necessary  for  science  that  this  law 
should  acquire  that  character  of  demonstration  which 
mere  experiments  alone,  however  precise,  cannot  confer, 
by  being  traceable  upwards  to  the  first  principles  of 
matter. 

Descartes  then  attempted  to  establish  his  law  of  re- 
fraction by  considerations  purely  mathematical ;  perhaps 
it  was  thus  also  that  he  discovered  it?  Fermat  com- 
bated the  demonstration  of  his  rival,  and  replaced  it  by 
a  method  more  rigorous,  but  which  had  the  serious  fault 

Vossius  states  that,  among  others,  the  contents  of  Snail's  MS.  were 
shown  to  Descartes. 

That  philosopher,  however,  in  a  manner  very  usual  with  him,  com- 
mences treating  the  subject  on  entirely  original  grounds;  and,  in  the 
course  of  a  purely  theoretical  speculation  deduces  the  same  law  of 
refraction  as  a  consequence  of  his  a  priori  principles  (DiojHrica,  1637, 
ch.  il.  §  9),  without  making  the  slightest  allusion  to  Snell.  Hence 
the  discovery  of  the  law  has  been  assigned  to  him,  especially  by 
French  writers.  It  is  to  be  observed,  however,  that  he  in  no  waj'  at- 
tempts to  found  his  deduction  on  any  comparison  of  experimental 
results.  Thus,  even  admitting  that  Descartes  is  entitled  to  the  estab- 
lishment of  the  law  as  a  iheoretical  deduction,  he  clearly  has  no  claim 
to  the  experimental  verification  of  it,  which  is  by  far  the  most  material 
point;  and  the  more  so  as  his  theory  is  based  on  the  assumption,  now 
proved  to  be  ftilse,  that  light  is  acceleraled  in  passing  through  the 
denser  medium. —  Translator. 


PRINCIPLE    OF    LEAST    ACTION.  189 

of  being  dependent  on  a  metaphysical  principle  of  which 
he  did  not  show  the  necessary  truth.*     Huyghens  ar- 

*  The  theoretical  principles  here  glanced  at,  are  those  connected 
■with  speculations  on  one  of  the  most  curious  points  presented  by  the 
theory  of  light;  which,  perhaps,  it  may  be  desirable  briefly  to  explain. 
Ptolemy  had  shown  that  when  light  is  reflected  from  any  surface,  the 
law  of  reflexion,  or  equality  of  angles,  is  precisely  that  which  causes 
light  to  pass  from  any  one  point  in  its  course,  before  incidence  to  any 
other  in  its  reflected  course,  bj'  the  sJiortesl  path  and  in  the  least  time, 
its  velocity  being  uniform  and  equal  before  and  after  reflexion. 

Fermat  extended  the  same  principle,  called  the  "  principle  of  least 
time,"  to  the  case  oi  refraction  according  to  the  law  of  sines,  provided 
"we  suppose  the  velocity  diminished  in  the  denser  medium :  that  is,  he 
showed  that  the  sum  of  the  times,  or  of  the  spaces  divided  by  the  veloci- 
ties, is  a  minimum. 

Huyghens,  adopting  the  theory  of  waves,  deduced  from  it  the  law 
of  the  sines;  and  as,  in  conformity  with  tliat  theory,  the  velocity 
must  be  diminished  in  the  denser  medium,  on  this  theoiy  the  principle 
of  "least  time  "  applies  to  the  case  of  refraction,  and  that  of  reflexion 
also  easily  follows  as  a  pai-ticular  case. 

On  the  other  hand,  on  the  molecular  theory,  the  law  of  refraction  is 
deduced  on  the  principle  of  attraction,  which  the  molecules  undergo 
in  the  medium,  and  it  is  a  necessary  consequence  that  the  velocity 
must  be  increased  in  the  denser  medium.  Maupertuis,  on  these  prin- 
ciples, attempted  an  analogous  investigation ;  but  here  it  was  neces- 
sary to  adopt,  not  the  principle  of  "least  time,"  but  that  of  "least 
action,"  or  that  the  sum  of  the  products  oJ'  the  spaces  and  velocities  is 
a  minimum ;  and,  on  this  view,  the  law  of  the  sines  equally  results  as 
that  which  fulfils  the  condition. 

This  refers  to  ordiuarj-  refraction :  when  the  same  inquiry  was  ex- 
tended to  double  refraction,  or  to  the  extraordinary'  ray,  more  complex 
considerations  were  introduced.  This  subject  is  fully  discussed  by 
Dr.  Young  in  his  Life  of  Fermat.  (  Wbi-ks,  ed.  Peacock,  vol.  ii.  p. 
584.)  The  same  principle  was  the  basis  of  Laplace's  investigation  of 
double  refraction,  of  which  ("  Sur  la  Loi  de  la  Refraction  Extraordi- 
naire, &c.,"  Journal  de  Physique,  1809)  Dr.  Young  produced  his  well- 
known  refutation  in  the  Quarterly  Review  for  the  same  year. 

In  the  case  of  ordinary  refraction,  the  investigation  is  very  simple. 
As  it  is  not  clearly  stated,  as  far  as  we  are  aware,  in  any  elementary 
treatise,  it  may  be  satisfactory  to  some  readers  to  have  it  briefly  put 
before  them. 

Let  any  lengths,  respectively,  of  the  incident  and  refracted  rays  be 


190 


FRESNEL. 


rived  at  the  result,  setting  out  from  the  ideas  he  had 
adopted  of  the  nature  of  light.     And,  lastly,  Newton  de- 

l  V,  described  with  the  velocities  vvf,  which  are  in  a  constant  ratio  to 
each  other;  and  in  times  which  will  be  —  ^.  Then,  on  the  prin- 
ciple  of  "least  time,"  the  condition  is, 

III         .  . 
1 =mmimum; 

V  VI  ' 

or,  differentiating  and  multiplying  by  v  v', 

V  dl  +  v  (III  =  0  .  .  .  .  (1). 
Then  if  X  be  the  surface  of  the  medium,  taking  equal  increments 
dxon  each  side  of  the  point  of  incidence,  and  dropping  perpendiculars 


to  give  corresponding  increments  dldV,  i  and  r  being  the  angles  of 
incidence  and  refraction,  we  have  geometrically  -, 


sm  J 

al^-  dll=:: 

ax 


dx 


■  (2); 


and  substituting  in  (1)  it  becomes 

d'  sin  i  — i;  sin  r  =  0, 


But,  as  i  is  necessarily  greater  than  ?',  it  follows  that  the  v  must  be 
greater  than  «':  or  the  law  of  the  sines  fulfils  the  condition  of  "least 
time"  on  the  wave  theory. 

On  the  other  hand,  the  principle  of  "  least  action"  requires,  instead 
of  equation  (1),  that  we  have 

lv-\-l'  vi  =  minimum, 
or  vdl+vldli=0: 

whence,  by  precisely  the  same  process,  there  results 
.     .      vi  . 


PRINCIPLE    OF    LEAST    ACTION.  191 

duced  it  from  the  principle  of  attraction,  because  that  law 

■which  can  only  agree  with  observation  provided  v'  be  greater  than  v, 
or  the  velocity  be  increased  in  the  refracting  medium,  which  agrees 
with  the  molecular  theory. 

On  either  supposition,  if  «  =  «/,  and  sin  r  positive,  the  case  becomes 
that  of  rejlexion,  and  we  have  i  =:  r,  which  is  the  law  of  reflexion, 
whence  Ptolemy's  conclusion  is  manifest  as  a  particular  case  of  the 
general  theory.  The  case  of  reflexion  is,  in  fact,  nothing  more  than  a 
geometrical  problem. 

Let  two  points  i  e,  be  given  without  a  given  straight  line  x  x/,  and 
let  o  be  the  point  in  that  line  at  which  straight  lines  drawn  from  i 


and  E  make  equal  angles  with  x  x'.  Then  taking  any  other  pairs  of 
lines  I  L,  L  E,  and  i  m,  m  k,  terminating  in  the  same  points  and  meet- 
ing X  X'  in  L  and  in  m,  they  will  each  form  unequal  angles  with  x  x' ; 
E  L  x'  greater  than  i  l  x,  and  r  m  x'  greater  than  i  m  x.  Let  i  m  and 
L  E  intersect  in  k. 

Then  we  have  the  angle  k  l  m  greater  than  i  l  x,  which  is 
greater  than  the  opposite  and  interior  i  M  l;  and  therefore  in  the 
triangle  k  l  m,  k  m  is  greater  than  k  l. 

In  the  limit,  when  m  approaches  l,  we  have  ultimately  i  k=i  l, 
and  K  R=M  k;  whence  i  l+l  k+k  r  is  less  than  i  k+k  m-|-m  k,  or 
the  pair  of  lines  nearest  to  o  are  together  less  than  the  more  remote. 
The  same  reasoning  will  apply  to  all  pairs  of  lines  on  either  side  of  o; 
therefore  the  lines  meeting  at  o  are  a  minimum. 

It  is  an  extension  of  this  principle  wliicli  forms  the  basis  of  the  in- 
vestigations of  Sir  W.  R.  Hamilton.  Observing  that  in  some  parallel 
instances  the  action  is,  in  fact,  not  a  case  of  minimum,  but  of  max- 
imum, lie  has  adopted  the  more  generic  term,  "stationary  action; " 
and  upon  this  has  based  his  fundamental  idea  of  the  "  characteristic 
function,"  by  the  aid  of  which  his  profound  analytical  system,  ap- 
plicable equally  in  questions  of  optics  and  dynamics,  is  constructed. 
For  an  admirable  exposition  of  the  general  principle  tlie  student 
should  consult  Sir  W.  E.  Hamilton's  paper  on  "  The  Paths  of  Light 
and  of  the  Planets"  in  the  Dublin  University  Review,  Oct.  1833. — 
Translaiar. 


192 


FRESNEL. 


occupied  the  attention  of  the  greatest  geometers  of  the 
seventeenth  century. 

Tlie  question  had  arrived  at  this  point,  when  a  travel- 
ler, returning  from  Iceland,  brought  to  Copenhagen  some 
beautiful  crystals  from  the  Bay  of  Roerford.  Their 
great  thickness  and  reaiarkable  transparency  rendered 
them  particularly  proper  for  experiments  on  refraction. 
Bartholinus  (1669),  to  wliom  they  were  sent,  took  care 
to  subject  them  to  different  trials  ;  but  what  was  his 
astonishment  when  he  perceived  that  the  light  divided 
itself  into  two  distinct  beams  of  precisely  equal  intensi- 
ties,— when  he  recognized,  in  one  word,  that  seen  through 
the  Iceland  spar  (which  has  been  since  found  in  many 
other  localities,  being  nothing  but  carbonate  of  lime)  all 
objects  appear  double  !  The  theory  of  refraction,  so 
many  times  recast,  had  now  need  of  a  new  examination. 
At  all  events  it  was  incomplete,  for  it  spoke  only  of  one 
ray,  and  two  were  here  seen.  Besides,  the  direction  and 
the  magnitude  of  the  deviation  of  the  two  rays  changed, 
apparently  in  the  most  capricious  manner,  when  we  passed 
from  one  face  of  a  crystal  to  another,  or  when  on  one  face 
the  dii-ection  of  the  incident  ray  varied.* 

Huyghens  surmounted  all  these  difficulties  ;  a  general 
law  was  found  to  comprehend  in  its  announcement  all  the 
lesser  details  of  the  phenomena  ;  but  this  law,  in  spite  of 
its  simplicity  and  elegance,  was  misconstrued.  Hypoth- 
eses had  been  for  so  many  ages  useless  or  faitliless  guides  ; 
they  had  been  so  long  considered  as  constituting  the  whole 
of  physics,  that,  at  the  epoch  of  which  I  speak,  experi- 
menters had  on  this  point  arrived  at  a  sort  of  reaction  ; 
and  in  such  reactions,  even  in  science,  it  is  rare  to  be 

*  See  above,  note,  p.  150. 


LAW   OF    DOUBLE    llEFRACTION.  193 

able  to  keep  a  just  mean.  Huyghens  had  given  his  law 
as  the  result  of  an  hypothesis  ;  men  rejected  it  therefore 
■without  examination.  The  measures  on  which  it  was 
founded  could  not  redeem  it  from  what  was  thought 
vicious  in  its  origin.  Newton  himself  took  part  among  its 
opponents  ;  and  from  this  moment  the  progress  of  optics 
■was  arrested  for  more  than  a  century.  Since  that  period, 
the  numerous  experiments  and  measures  of  two  of  the 
most  celebrated  members  of  this  Academy,  WoUaston 
and  Mains,  have  replaced  the  law  of  Huyghens  in  the 
rank  to  which  it  is  entitled.* 

*  Newton  had  rejected  Huyghens's  law,  and  substituted  one  founded 
on  measures  of  his  own.  In  1788  Haiiy  repeated  the  measurements, 
and  showed  that  Huj'ghens's  rule  was  far  more  accurate  than  New- 
ton's. In  1802  Wollaston  repeated  similar  observations  by  his  new 
method,  in  ignorance  of  Huyghens's  law;  but  found  them  well  repre- 
sented when  that  law  was  pointed  oi;t  to  him — probably  by  Dr.  Young, 
as  the  circumstance  is  stated  by  him  in  an  article  in  the  Quarterly 
Revieto,  Nov.  1809,  p.  338. 

Some  idea  may  be  given  of  the  simple  geometrical  construction  de- 
termining the  direction  of  the  extraordinary  ray  which  results  from 
Huyghens's  theory,  as  follows:  Supposing  portions  of  the  concentric 
sphere  and  spheroid  within  the  crj-stal,  whose  axis  a  coincides  with 
the  axis  of  revolution  of  the  spheroid;  and  conceiving  a  second  spher- 
ical surface  concentric,  and  of  greater  radius,  as  that  which  would 
have  been  the  wave  surface  if  the  velocity  had  remained  undimin- 


194  FRESNEL. 

During  the  long  discussions  which  took  place  among 
physicists  on  the  mathematical  law  according  to  which 
double  refraction  is  produced  in  Iceland  spar,  the  exist- 
ence of  the  second  ray  was  generally  considered  as  an 
anomaly  affecting  half  the  incident  light ;  the  other  half, 
it  was  said,  obeyed  the  old  law  of  refraction  laid  down  by 
Descartes  :  the  carbonate  of  lime,  in  its  crystallized  state, 
then,  enjoys  certain  particular  properties,  but  without 
losing  those  which  all  ordinary  transparent  media  i>os- 
sess.  All  this  was  exact  in  the  instance  of  tlie  Iceland 
spar,  and  it  seemed  as  if  it  mi^lit  witliont  hazard  be 
asserted  generally ;  but  in  fact  those  who  maintained 
this  deceived  themselves.  There  are  crystals  in  which 
the  principle  of  ordinary  refraction  is  not  veritied  ;  and 
in  which  the  two  rays  into  which  the  incident  light  divides 
itself  both  undergo  anomalous  refractions,  where  the  law 
of  Descartes  does  not  indicate  the  course  of  either  ray. 

When  Fresnel  for  the  first  time  published  this  unex- 
pected result,  he  had  as  yet  verified  it  only  by  the  aid  of 
an  indirect  method,  i-emarkable  for  the  strange  circum- 
stance that  the  refraction  of  the  rays  was  deduced  from 
experiments  in  which  no  refraction  took  place.  Thus 
our  colleague  found  more  than  one  incredulous  reader. 
The  singularity  of  the  discovery,  perhaps,  demanded 
some  hesitation :  perhaps  also  in  the  eyes  of  some  per- 
sons, it  had  the  fault,  like  the  law  of  Huyghens,  of  being 
the  fruit  of  an  hypothesis.  However  it  may  have  been, 
Fresnel  met  the  difficulty  boldly.  By  showing  that  in  a 
parallelopiped  of  topaz,  ibrmed  of  two  prisms  of  the  same 

ished;  tlieu  from  the  extremity  t  of  the  incident  ray  i  as  if  produced 
to  meet  this  sphere,  drawing  tangent  planes  to  the  spliere  and  spheroid 
respectively,  the  points  of  contact  will  give  the  position  of  the  ordinary 
and  extraordinary  rays  o  and  e.  See  Peacoclv's  Life  of  Young,  p.  373. — 
Translator. 


BIAXIAL    CRYSTALS.  195 

angle,  opposed,  no  ray  passes  between  the  opposite  and 
parallel  faces  without  undergoing  deviation,  he  rendered 
all  objections  vain.* 

*  The  paradoxical  mention  of  proofs  of  refraction,  ■where  no  refrac- 
tion takes  place,  may  need  a  brief  explanation. 

Fresnel's  experiment,  here  referred  to,  was  performed  by  means  of 
the  simple  interference  of  two  rays  produced  by  reflexion  from  plane 
mirrors  very  little  inclined  from  the  same  plane,  or  by  transmission 
through  a  very  obtuse-angled  prism.  If,  in  the  path  (as  explained  in 
a  subsequent  note)  of  each  of  the  two  interfering  rays,  plates  of  glass 
of  exactly  the  same  thickness  are  interposed,  the  position  of  the  stripes 
remains  unaltered;  but  if  the  plates  be  cut  from  a.  biaxial  crystal  in 
different  directions  with  respect  to  its  axis,  but  still  of  exactly  the 
same  thickness,  even  if  we  employ  those  rays  which  correspond  to  the 
ordinary  rays  in  Iceland  spar,  there  will  be  a  displacement  of  the 
stripes,  showing  a  difference  of  velocity  or  refraction,  in  these  rays, 
on  the  principle  hereafter  explained,  (see  note  infra.) 

The  more  direct  experiment  alluded  to  consists  in  this:  Fresnel  cut 
two  prisms  in  different  directions  from  the  same  crystal  of  topaz, 
which,  being  cemented  together  with  their  axes  in  one  line,  were 
ground  together  to  exactly  the  same  angle,  and  the  whole  achroma- 
tized by  another  opposed  prism.  On  looking  through  the  two  prisms 
thus  fixed  side  by  side  at  a  line  of  light,  that  line  was  seen  to  be  bro- 
ken at  the  junction,  indicating  different  refractions  in  the  two. 

The  law  of  Huyghens,  or  the  construction  of  the  sphere  and  sphe- 
roid, was  found  to  hold  good  not  only  in  Iceland  spar,  but  in  many 
Other  doubly  refracting  crystals.  But  these  were  all  characterized  by 
possessing  only  one  axis  or  line  along  which  there  was  no  double  re- 
fraction, and  which,  by  the  aid  of  polarized  light,  is  easily  detected  as 
forming  the  centre  of  the  rings. 

Sir  D.  Brewster,  in  examining  a  vast  varietj'  of  crystals,  discovered 
a  class  in  which  there  was  not  one  such  axis,  but  tivo,  and  in  which 
the  rings  consequently  assumed  new  and  more  complex  forms,  being 
either  arranged  in  two  separate  sets  if  the  axes  were  distant,  or  in 
coalescing  curves  if  they  were  close. 

For  biaxial  crystals  Huyghens's  law  will  not  apply.  The  incident 
ray  is  divided  into  two;  but  neither  of  them  follows  the  law  of  the 
sines  represented  by  the  sphere  in  his  construction.  One  of  the  rays 
is,  indeed,  usually  less  subject  to  deviation  than  the  other,  and  thus, 
for  convenience,  is  still  often  called  the  ordinary  ray;  but  both  are,  in 
strictness,  extraordinary  rays. 


196  FRESNEL. 

Those  physicists  (I  could  here  cite  the  names  of  some 
of  the  most  celebrated)  who  have  sought  to  include  in  a 

Hence  the  necessity  for  a  more  comprehensive  theor}'.  As  Huy- 
ghens  had  constructed  sucli  a  theory  by  means  of  an  independent 
sphere  and  spheroid,  Fresnel  not  only  generalized  the  construction  by 
a  method  giving  two  curved  surfaces  of  higher  forms,  but  he  did  what 
Huvghens's  method  did  not  effect,  even  in  the  simple  case  which  he 
considered  — he  showed  also  a  necessary  connection  between  tlie  two 
surfaces  •  they  were  in  fact  not  two,  but  portions  of  one  surface — parts 
of  the  geometi-ical  representation  of  the  same  algebraic  equation,  or, 
in  the  h^nfuao'e  of  mathematicians,  "a  curve  surface  of  two  sheets." 
Thus  Frcsnel's  theory  showed  not  only  the  laws  by  which  each  ray 
was  refracted,  but  also  why  there  must  be  two  rays. 

Of  this  more  generalized  mathematical  investigation,  the  greater 
part  of  the  steps  were  omitted  by  Fresnel  in  his  memoir,  as  being  of 
too  complicated  and  tedious  a  nature  for  the  patience  of  his  readers; 
he  presents  only  the  conclusions,  which  are  derived  from  certain  sup- 
positions with  respect  to  the  elasticity  of  the  ether,  as  being  different 
in  different  directions  within  the  crystal,  and  ultimately  lead  to  an 
algebraic  equation,  representing  a  curved  surface  of  the  fourth  order, 
consisting  of  two  sheets  or  portions,  as  the  general  form  assumed  by 
the  waves,  but  which  in  certain  cases,  as  in  calc  spar,  is  reducible  to 
the  simpler  form  of  the  sphere  and  spheroid  of  Huyghens. 

For  a  connected  view  of  these  investigations  the  reader  is  referred 
to  Professor  Powell's  Treatise  on  the  Undulatory  Theory,  fc.  page  48. 
London,  1841. 

The  mathematical  investigation  has  since  called  forth  much  eluci- 
dation, especially  in  supplying  the  suppressed  processes  of  Fresnel,  ia 
which  the  analysis  of  Mr.  A.  Smith,  as  well  as  those  of  Sir  J.  Lub- 
bock, Professor  Sylvester,  Sir  W.  K.  Hamilton,  and  others,  have  been 
eminently  successful;  while  the  last-named  mathematician  pointed 
out  the  very  curious  consequence  that  this  surface,  mathematically 
speaking,  presents,  at  the  extremities  of  the  axis,  conoidal  cusps, — that 
is  depressions  of  a  pointed  funnel  shape, — which,  physically  inter- 
preted, would  show  that  a  ray  passing  along  that  direction  ought  to 
emerge  no  longer  a  single  ray,  but  spread  out  in  a  conical  surface 
whose  surface  would  not  be  a  point  of  light,  but  a  ring  with  a  dark 
central  space.  This  extraordinary  prediction,  so  wholly  unlike  any 
thing  hitherto  imagined,  was,  however,  fully  verified  by  the  observa- 
tions of  Dr.  Lloyd  on  a  crystal  of  aragonite ;  the  phenomenon  being 
known  by  the  name  of  '■^  conical  reiva.ct\on."— Translator. 


DOUBLE    REFRACTION.  197 

single  rule  all  the  possible  cases  of  double  refraction, 
were  thus  misled,  for  they  all  admitted,  as  a  fact  of 
which  no  one  could  doubt,  that  for  half  the  light,  for  the 
rays  called  "ordinary  rays,"  the  deviation  ought  to  be 
the  same  at  the  same  incidence  in  whatever  direction 
the  plane  of  incidence  cut  the  crystal.  The  true  law  of 
these  complicated  phenomena — the  law  which  includes, 
as  particulai'  cases,  the  laws  of  Descartes  and  of  Huy- 
ghens — is  due  to  Fresnel.  This  discovery  required  in 
an  eminently  high  degree  the  union  of  a  talent  for  exper- 
iment with  the  genius  of  invention. 

I  freely  admit  that  the  phenomena  of  double  refraction 
recently  analyzed  by  Fresnel,  and  tlie  laws  which  con- 
nect them,  are  not  exempt  from  a  certain  complexity. 
This  is  indeed  a  subject  of  regret — almost,  I  might  say, 
of  lamentation — among  some  idle  minds,  who  would  wish 
to  reduce  every  science  to  those  superficial  notions  of 
which  they  might  make  themselves  masters  by  a  few 
hours'  work.  But  does  not  every  one  see  that  with  such 
ideas  the  sciences  would  not  make  any  pi'ogress  ;  that  to 
neglect  such  phenomena  because  one  feeble  intellect  may 
experience  some  trouble  in  grasping  them,  would  be  to 
be  false  to  our  vocation,  and  that  thus  we  should  often 
allow  the  most  important  discoveries  to  pass  by  us. 

Tims  astronomy,  while  limited  to  a  knowledge  of  the 
constellations,  and  to  some  insignificant  remarks  on  the 
risings  and  settings  of  the  stars,  was  within  the  capacity 
of  minds  of  any  class  :  but  could  we  then  call  it  a  science  ? 
From  that  time  till  after  the  most  colossal  labour  which 
one  man  ever  went  through, — Kepler  had  substituted 
elliptic  motions  not  uniform,  for  the  circular  and  regular 
motions  which,  according  to  the  ancients,  prevailed  in  the 
planets, — his  contemporaries  might  with  equal  right  have 


198  FRESNEL. 

complained  of  complexity.  But  again,  some  time  after, 
in  the  hands  of  Newton,  these  motions,  complex  in  ap- 
pearance, became  the  basis  of  the  greatest  discoveries  of 
modern  times,  of  a  principle  as  simple  as  it  is  fertile ; 
they  served  to  prove  that  every  planet  is  governed  in  its 
elliptic  course  by  a  simple  force,  by  an  attraction  emanat- 
ing from  the  sun. 

Those  observers  again,  who,  in  their  turn  refining 
upon  Kepler,  showed  that  simple  elliptic  motions  would 
not  suffice  to  represent  the  true  paths  of  the  planets, 
did  not  simplify  the  science.  But  besides  that  the 
derangement  (known  under  the  name  of  perturbations) 
would  not  the  less  have  existed  if,  in  the  dislike  of  all 
complexity,  we  had  obstinately  determined  to  shut  our 
eyes  to  them,  I  ought  to  "ay,  that  in  studying  them  with 
cai'e  we  have  been  conducted,  among  many  other  impor- 
tant results,  to  the  means  of  comparing  the  masses  of  the 
different  bodies  of  which  our  solar  system  is  composed  ; 
and  that  if  at  the  present  day  we  know,  for  example,  that 
it  requires  not  less  than  350,000  times  the  globe  of  the 
earth  to  form  a  weight  equal  to  that  of  the  sun,  we  owe 
it  to  the  observation  of  those  very  small  inequalities, 
which  those  would  certainly  have  neglected,  who  at  all 
risks  would  admit  nothing  but  simple  phenomena. 

Without  extending  these  remarks  farther,  I  may  then 
admit  that  optics  would  be  a  more  easy  science,  more  at 
the  command  of  the  generality  of  men,  more  susceptible 
of  demonstration  in  public  lectures,  before  the  extension 
of  it  which  has  been  made  in  our  times.  But  this  exten- 
sion is  a  real  source  of  riches  ;  it  has  given  occasion  for 
the  most  curious  applications ;  it  has  thence  afforded 
those  indications  of  impossibilities  in  certain  theories  of 
light,  which  may  claim  to  rank  among  discoTeries ;  for 


DOUBLE    KEFRACTION.  199 

in  the  search  after  causes,  we  are  often  reduced  to  pro- 
ceed by  the  method  of  exclusion,  and  in  this  point  of  view, 
there  is  no  experiment  which  is  witliout  use  ;  we  can- 
not muhiply  them  too  much.  That  universal  genius,  Vol- 
taire, who  often  took  pleasure  in  concealing  a  profound 
meaning  under  a  burlesque  form,  compared  a  theory  to  a 
mouse,  which  passes,  he  said,  through  nine  holes,  but  is 
caught  in  the  tenth.  It  is  in  multiplying  indefinitely  the 
number  of  these  holes,  or  to  speak  in  a  manner  less  triv- 
ial, the  number  of  tests  which  a  theory  ought  to  satisfy, 
that  astronomy  is  placed  in  the  rank  which  it  occupies 
in  the  estimation  of  men,  and  that  it  has  become  the  first 
of  the  sciences.  It  is  in  following  the  same  route  that 
we  sliall  be  able  in  like  manner  to  give  to  other  branches 
of  science  the  character  of  evidence  which  they  yet  want 
in  some  respects.  In  every  science  of  observation  we 
must  distinguish  the  facts,  the  laws  which  connect  them, 
and  the  causes.  Often  the  dilTiculties  of  the  subject 
arrest  experimenters  after  the  first  step  ;  hardly  ever  do 
they  allow  them  to  pass  freely  to  the  third.  The  pro- 
gress which  Fresnel  made  in  the  two  former  respects,  in 
the  study  of  double  refraction,  by  natural  consequence, 
led  him  to  inquire  on  what  so  singular  a  phenomenon 
depended.  And  here  again  he  obtained  striking  suc- 
cess. But  pressed  for  time,  I  can  only  make  known  the 
most  prominent  of  his  results. 

When  Huyghens  published  his  Traitt  de  la  Lumiere, 
there  were  only  known  two  crystals  possessing  double 
refraction, — carbonate  of  lime  and  quartz.  At  present  it 
would  be  far  shorter  to  enumerate  those  which  have  not 
this  property,  than  those  which  have  it.  Formerly,  it 
was  necessary  that  a  substance  should  distinctly  show 
double  images,  to  allow  us  to  assimilate  it  with  Iceland 


200  FRESNEL. 

spar.  Whenever  the  separation  of  the  two  rays  was  so 
small  as  to  escape  detection  by  the  eye,  the  observer 
remained  in  doubt  and  did  not  venture  to  pronounce  it 
doubly  refractive.  Now,  however,  by  the  aid  of  a 
method  which  a  member  of  the  Academy  has  pointed 
out,*  the  existence  of  double  refraction  manifests  itself 
by  characteristics  quite  independent  of  the  separation  of 
the  two  images.  No  substance,  however  thin  it  may  be, 
possessed  of  this  property,  can  escape  this  new  mode  of 
examination.  But,  if  it  were  certain  that  double  refrac- 
tion could  not  exist  without  our  perceiving  the  very 
manifest  phenomena  on  which  this  method  is  founded,  it 
would  not  appear  equally  incontestable  that  it  ought 
necessarily  to  accompany  them  ;  and  a  doubt  in  regard 
to  this  might  seem  the  more  natural  since  the  author  of 
this  method  has  himself  found  certain  jjlates  of  glass 
which,  without  separating  the  images  in  a  perceptible 
degree,  yet  give  birth  to  all  the  phenomena  in  question  : 
— since  a  distinguished  philosopher  of  Berlin,  M.  See- 
beck,  afterwards  proved  that  all  glass  rapidly  cooled 
enjoyed  the  same  property  ; — and  since,  lastly,  a  very 
able    experimenter    of    Edinburgh    produced    the    same 

*  The  author  here  alludes  to  his  own  discovery  of  the  polarized 
coloui\s,  made  also  quite  independently  by  Brewster  about  the  same 
time.  These  tints  are  now  familiar  to  most  persons  by  means  of  the 
little  instrument  called'tlie  polariscope.  By  placing  a  plate  of  sele- 
nite,  mica,  &:c.,  far  too  thin  to  exhibit  any  separation  of  images,  in 
polarized  light,  and  viewing  it  through  an  analyzer,  these  brilliant 
tints  convey  distinct  evidence  of  the  existence  of  that  propertj^,  since 
they  are  shown  iheorclicaUy  to  depend  solely  upon  its  existence,  how- 
ever insensibly  small  its  amount  may  be.  It  therefore  seems  impor- 
tant for  the  verification  of  theory,  to  show  independently  its  existence 
in  any  substances  which  exhibit  the  tints.  Glass  ordinarily  possesses 
no  such  power;  but  plates  of  unannealed  glass  exhibit  the  tints. 
Hence  the  importance  of  the  experiments  mentioned  to  show  its 
existence  directlv. —  Transhilor. 


DOUBLE    REFRACTION.  201 

phenomena  by  compressing  pieces  of  glass  with  groat 
force  in  certain  directions.  To  show  that  a  piece  of 
ordinary  glass,  thus  modified  by  cooling  or  compression, 
always  really  separates  the  light  into  two  rays, — and  to 
render  this  separation  incontestably  evident,  was  the 
important  problem  which  Fresnel  proposed  to  himself, 
and  which  he  resolved  in  his  usual  happy  manner. 

By  placing  in  the  same  line,  and  in  a  frame  of  iron 
carrying  powerful  screws  ingeniously  arranged,  a  number 
of  prisms  of  glass,  which  by  these  screws  were  subjected 
to  very  powerful  pressure,  Fresnel  caused  a  manifest 
double  refraction  to  appear.  In  an  optical  point  of  view 
this  assemblage  of  pieces  of  common  glass  became  a  true 
Iceland  crystal ;  but  here  the  separation  of  the  images, 
and  all  the  other  properties  which  flow  from  it,  resulted 
exclusively  from  the  action  of  the  compressing  screws. 
Now  this  action,  carefully  analyzed,  ought  only  to  pro- 
duce one  effect,  a  close  approach  to  each  other  of  the 
molecules  of  the  glass  in  the  direction  of  the  pressure  ; 
while,  in  the  direction  perpendicular  to  this,  the  mole- 
cules preserve  their  original  distances.  Can  we  then 
doubt,  after  this  remarkable  experiment,  that  an  analo- 
gous arrangement  of  the  molecules  produced  during  the 
act  of  crystallization  was  thus  the  general  cause  of  the 
double  refraction  in  carbonate  of  lime,  quartz,  and  all 
minerals  of  the  same  kind.  If  we  consider  with  atten- 
tion the  ingenious  apparatus,  by  the  aid  of  which  Fres- 
nel, in  thus  giving  an  artificial  double  refraction  to  ordi- 
nary glass,  has  caused  so  great  a  step  to  be  made  in  the 
science,  we  are  struck  with  the  great  amount  of  aid 
which  the  spirit  of  invention  borrows,  whether  from  the 
knowledge  of  the  arts,  or  from  that  manual  dexterity 
which  has  been  so  well  described  by  Franklin  when  he 

9* 


202  FRESNEL. 

required  of  experimenters  lo  be  able  to  saw  with  a  file, 
and  to  file  with  a  saw. 

Want  of  time  will  not  permit  me  to  refer  here  to 
other  various  labours  of  our  colleague  equally  relative  to 
the  refraction  of  light,  and  of  which  I  do  not  exaggerate 
the  importance  in  saying  that  they  would  alone  suffice 
to  establish  a  reputation  equal  to  that  of  many  physi- 
cists of  the  first  eminence.  I  hasten  to  pass  on  to  an 
optical  theory  not  less  interesting,  and  altogether  of 
modern  date ;  which  is  designated  by  the  name  of  the 
theory  of  "Interferences."  It  will  furnish  me  with  new 
occasions  to  render  apparent  the  astonishing  perspicuity 
of  Fresnel's  mind,  and  the  inexhaustible  resources  of  his 
inventive  genius. 

INTERFERENCES. 

The  very  name  of  "  interference  "  has  as  yet  hai'dly 
emerged  beyond  the  precincts  of  scientific  societies,  and 
yet  I  know  not  whether  any  branch  of  human  knowl- 
edge presents  phenomena  more  varied,  more  curious, 
more  strange.  Let  us  endeavour  to  disengage  the 
capital  fact  which  pervades  this  whole  theory  of  the 
technical  language  in  which  it  is  commonly  enveloped, 
and  we  may  hope  it  will  before  long  be  admitted  that  it 
deserves  in  a  high  degree  to  attract  public  attention. 

I  will  suppose  that  a  ray  of  the  sun's  light  falls 
directly  on  any  screen,  as  for  instance  on  a  sheet  of  fine 
white  paper.  The  part  of  the  paper  on  which  the  ray 
falls  will  of  course  be  brightly  illuminated  ;  but  it  might 
seem  incredible  if  we  assert  that  it  depends  on  the  ex- 
perimenter to  render  this  spot  perfectly  dark  without 
stopping  the  ray  or  touching  the  paper. 

What  then  is  the  magical   process  which  allows  us  to 


INTERFERENCES.  203 

transform  at  pleasure  light  into  darkness,  day  into  night? 
The  process  will  excite  more  surprise  than  even  the 
result.  It  consists  in  directing  upon  the  paper,  but  by  a 
route  very  slightly  different,  a  second  ray  of  light,  which, 
taken  by  itself,  would  also  have  brilliantly  illuminated 
it.  The  two  rays  in  mixing  together,  it  might  be  ex- 
pected, would  produce  a  yet  more  brilliant  illumination ; 
no  doubt,  it  would  seem,  could  exist  on  this  point ;  but 
in  point  of  fact,  under  certain  conditions,  they  entirely 
destroy  each  other,  and  we  find  ourselves  to  have  created 
darkness  by  adding  one  portion  of  light  to  another. 

A  new  fact  requires  a  new  term  ;  this  phenomenon, 
in  which  two  rays  in  mixing  together  destroy  each 
other,  either  wholly  or  partially,  is  termed  '^  an  inter- 
ference." 

Grimaldi  had  long  ago  (before  1665)  formed  some 
notion  of  the  action  which  one  beam  of  light  may  exer- 
cise upon  another  ;  but  in  the  experiment  which  he  cites 
this  action  was  but  obscurely  manifested;  and,  besides 
this,  the  conditions  which  were  essential  to  its  produc- 
tion had  not  been  pointed  out,  and  thus  no  other  experi- 
menter followed  up  the  inquiry. 

In  searching  after  the  cause  of  the  iridescent  colours 
with  Avhich  soap  bubl:)les  shine  so  brilliantly,  Ilooke 
believed  that  they  were  the  result  of  interferences  ;  he 
even  very  ingeniously  pointed  out  some  of  the  circum- 
stances which  cause  their  production  ;  but  it  was  a  theory 
destitute  of  actual  proofs.  And  as  Newton,  who  knew 
of  this  theory,  did  not  deign  even  once  in  his  great  work 
to  discuss  it  critically,  it  remained  more  than  a  century 
in  oblivion.* 

*  The  silence  of  Newton  as  to  Hooke's  attempt  at  explaining  tlie 
colours  of  films  by  the  wave  theoi-}-  may,  we  conceive,  be  fully  ex- 


204  FRESNEL. 

The  complete  experimental  demonstration  of  the  fact 
of  interferences  will  always  be  the  principal  title  of 
Dr.  Thomas  Young  to  the  recognition  of  posterity.  The 
researches  of  this  illustrious  physicist  (whose  recent  loss 
the  sciences  have  to  deplore)  had  already  led  to  the 
general  principles  which  I  do  not  think  I  ought  here  to 
abstain  from  announcing,  although  the  genius  of  Fresnel 
seized  upon  them,  extended  them,  and  showed  their 
great  fertility.* 

plained  from  the  extremely  vague  nature  of  that  explanation;  it,  in 
fact,  amounted  to  no  more  than  a  general  notion  that  some  such  peri- 
odical action  might  be  occasioned  by  a  concurrence  of  waves  or  pul- 
ses. It  did  not  amount  to  a  theory;  it  had  no  reference  to  measures 
of  the  phenomenon,  and  indicated  nothing  like  a  law.  At  the  time 
Hooke  does  not  appear  to  have  been  aware  of  the  composition  of  white 
light,  and  thus  all  accurate  analysis  of  the  phenomenon  was  out  of 
the  question.  Newton  pursued  the  subject  on  professedly  experi- 
mental grounds  alone ;  it  was  not  his  plan  to  enter  on  any  theoreti- 
cal considerations ;  he,  therefore,  could  not  be  expected  to  refer  to 
Hooke's,  which  must  necessarily  have  seemed  to  him  wholly  gratui- 
tous, and  even  visionary. —  Translator. 

*  Young's  investigations  of  diffraction  was  rather  general,  and 
qualitative,  though  the  demonstration  as  to  the  natui-e  of  the  effect 
was  perfectly  conclusive;  but  the  later  researches  of  Fresnel  carried 
out  the  subject  to  a  quantitative  determination.  This  being  made  to 
include  the  combined  effect  of  an  infinite  number  of  interferences 
acting  at  every  point,  involved  the  use  of  the  higher  calculus;  and  the 
result  was  established  by  means  of  integrations  giving  the  intensity 
of  lin-ht  at  all  parts  of  the  screen  or  image.  This  remark  applies  not 
merely  to  the  particular  case  of  diffraction,  but  to  that  of  thin  plates, 
and  other  analogous  cases,  in  which  the  principle  of  interference  is 
applied.  This  analytical  extension  constituted  one  of  the  most  char- 
acteristic excellences  of  Fresnel's  researches.  In  an  experimental 
point  of  view,  Fresnel's  researches  are  characterized  by  scarcely  less 
improvements.  The  most  material  modifications  he  introduced  were 
those  of  (1.)  viewing  the  image  of  the  stripes  directly  by  an  eye  lens, 
instead  of  throwing  them  on  a  screen; — (2.)  discarding  any  interposi- 
tion of  an  opaque  body,  and  causing  two  rays  simply  to  act  on  each 
other,  by  causing  the  sun's  light  diverging  from  a  minute  aperture  or 


FRESNEL  S    METHOD. 


205 


Two  rays  cannot  destroy  each  other  unless  they  have 
a  common  origin ;  that  is  to  say,  unless  they  both  em- 
anate from  the  same  particle  of  an  incandescent  body. 
The  rays  from  one  side  of  the  sun's  disk  do  not  interfere 
"with  those  from  the  other  side,  or  from  the  centre. 

Among  the  thousands  of  rays  of  different  tints  and 
refrangibilities  of  which  white  light  is  composed,  those 
only  are  capable  of  interference  which  possess  colours 
and  refrangibilities  identically  the  same  ;  thus,  in  what- 
ever manner  we  take  them,  a  red  ray  will  never  destroy 
a  green  ray. 

With  respect  to  rays  of  the  same  origin  and  the  same 
colour,  they  are  constantly  mixed  and  superposed  with- 
out influencing  each  other ;  they  produce  effects  repre- 
sented by  the  sum  of  their  intensities, — if  at  the  moment 
of  their  crossing  each  other  they  have  gone  through 
routes  perfectly  equal  in  length. 

An  interference  can  alone  take  place  when  the  routes 
through  which  the  rays  have  passed  are  unequal ;  but  it 

the  focus  of  a  small  lens,  to  be  divided  into  two  streams,  either  by 
reflection  from  two  mirrors  very  little  inclined  to  each  other,  or  trans- 


mission throurrli  a  very  obtuse  angled  prism.  Here  the  interference 
stripes  are  seen  by  the  eye-ghiss  in  the  middle  of  the  mixed  light  in 
the  greatest  purity  and  intensity  of  alternation  of  brightness  and 
darkness. —  Translator. 


206  FRESNEL. 

is  not  every  inequality  of  this  kind  which  will  necessa- 
rily produce  a  destruction  of  light ;  such  difference  may, 
on  the  contrary  cause  the  rays  to  reinfore  each  other. 

But  when  we  know  what  is  the  least  difference  of 
route  gone  through,  at  which  the  rays  may  be  super- 
posed tvithoiit  injluencing  each  other,  we  then  obtain  all 
the  other  differences  of  route  which  give  the  same  result 
in  a  very  simple  manner  ;  for  it  suffices  to  take  the 
double,  the  triple,  the  quadruple,  &c.,  i.  e.  every  whole 
multiple,  of  the  first  number  to  give  them. 

If  we  have  noted  in  like  manner  the  least  difference 
of  route  which  pi'oduces  complete  destruction  of  the  two 
rays,  every  odd  whole  multiple  of  this  first  number  will 
also  be  the  indication  of  a  like  destruction. 

As  for  differences  of  route  which  are  not  numerically 
comprised  either  in  the  first  or  in  the  second  of  the 
above  series,  they  correspond  only  to  partial  destruc- 
tions of  the  light,  or  mere  weakening  of  its  intensity. 

These  series  of  numbers,  by  aid  of  which  we  can  tell 
whether  two  rays  at  the  moment  of  intersection  ought  to 
interfere  or  merely  to  combine  without  influencing  each 
other,  have  not  the  same  values  for  the  differently  col- 
oured rays ;  the  smallest  values  belong  to  the  violet  rays, 
the  greatest  to  the  red,  and  the  intermediate  values  to 
the  intermediate  rays.  It  results,  that  if  two  white  rays 
cross  at  a  certain  point,  it  may  be  possible  that  in  the 
infinite  series  of  differently  coloured  rays  of  which  that 
light  is  composed,  the  red,  for  example,  alone  may  be 
destroyed  and  disappear,  and  thus  the  point  of  concourse 
may  appear  green,  as  being  the  white  light  deprived  of 
its  red  component. 

Interference,  then,  which  in  homogeneous  light  pro- 
duces only  changes  in  intensity,  will  manifest  itself  when 


DIFFERENCES    OF    ROUTE. 


207 


we  operate  with  white  hght  in  phenomena  of  colora- 
tion. In  the  course  of  such  singular  results  we  may, 
perhaps,  be  curious  to  find  the  numerical  value  of  these 
differences  of  route,  so  often  mentioned,  and  which  place 
two  rays  in  (he  conditions  either  of  accordance  or  com- 
plete destruction.  I  will  mention,  then,  that  for  red  light 
we  pass  from  the  one  of  these  conditions  to  the  other 
when  we  make  the  difference  of  route  amount  to  three 
ten  thousandths  of  a  millimetre.* 

*  The  numerical  values  of  the  differences  of  route,  as  Arago  ex- 
presses it,  or  the  connection  of  the  wave  lengths  for  different  rays 
with  the  intervals  between  the  stripes  is  easily  investigated;  and  the 
latter  being  readily  susceptible  of  accurate  micrometrical  measure- 
ment, the  former  may  be  deduced.  Let  two  rays  be  inclined  at  a  very 
small  angle  2  6.  Then  the  crossings  of  the  waves  will  give  rise  to  a 
set  of  bright  and  dark  points  at  +,  o,  &c.,  according  as  like  or  unlike 
portions  meet.  Let  c  be  the  interval  between  two  successive  bright 
points  and  X  the  wave  lengths.  Then  we  have  obviously  the  rela- 
tion — 

C  =  r-    cot       d 


208  FRESNEL. 

In  order  that  the  difference  of  route  alone  may  deter- 
mine whether  two  rays  of  the  same  origin  and  the  same 
colour  shall  reinforce  or  destroy  each  other,  it  is  neces- 
sary that  both  should  be  traversing  the  same  medium, 
solid,  liquid,  or  gaseous.  If  it  be  not  thus,  we  must  then 
also  take  into  account   (as  a  member  of  the  Academy* 

and  similarly  for  successive  values  of  c,  measured  from  the  central 
point,  involving  successive  multiples  of  1\  and  if  a  plate  of  glass 
whose  refraction  index  is  fi,  be  interposed  in  the  path  of  one  of  the 
rays,  whose  thickness  is  i,  the  difference  of  retardation  will  be  equiv- 
alent to  a  difference  of  route  expressed  by 

and  this  being  substituted  for  the  particular  multiple  of  1,  which 
expresses  the  difference  of  routes  in  the  first  formula,  gives  for  the 
displacement 

c=  t(u  —  1) . 

2 

It  may  be  added  that  the  values  of  the  wave  lengths  determined  by 
this  method  from  the  observed  widths  of  the  stripes,  or  by  others  of 
an  analogous  kind,  give  results  exactly  accordant  with  those  long  ago 
assigned  by  Newton  for  the  length  of  the  "fits"  derived  from  his 
measures  of  the  diameters  of  the  coloured  rings,  and  by  which,  from 
the  known  curvatures  of  the  lenses,  he  determined  the  thickness  of 
the  films,  and  thence  the  lengths  of  the  "  ?i\9,:'— Translator. 

*  The  retardation  of  one  of  the  rays,  and  consequent  shifting  of  the 
stripes,  is  here  alluded  to,  which  was  the  discovery  of  Arago;  being 
in  the  first  instance  exhibited  by  the  total  disappearance  of  the  stripes, 
as  must  be  the  case  if  the  plate  of  glass  have  more  than  almost  an  in- 
finitesimal thickness.  The  fact  was  first  announced  as  a  sort  of  par- 
adox, that  as  Young  had  found  the  stripes  entirely  disappear  by  inter- 
posing an  opaque  screen  on  one  side  only,  so  Arago  produced  the  same 
effect  with  a  perfectly  transparent  screen.  In  order  to  explain  this 
effect,  let  us  conceive  the  simple  case  of  two  rays  of  white  light,  made 
to  interfere  as  in  Fresnel's  experiment. 

The  slightest  consideration  will  show  that,  at  the  middle  point  of 
the  mixture  of  light,  two  concurring  rays,  of  whatever  primitive  col- 
our or  wave  length,  have  gone  through  precisely  the  same  length  of 
route;  and  thus  the  central  stripe  and  its  immediate  neighbour  on 
each  side,  are  absolutely  white  and  black,  and  perfectly  defined;  but 
in  proportion  as  we  recede  from  this  point  on  either  side,  the  differ- 


RETARDATION. 


209 


has  proved  by  incontestable  experiments)  the  thickness 
and  the  refractive  power  of  the  body  through  which  the 

ences  of  route  of  the  concurring  [rajs  become  necessarily  greater. 
But  wliite  light  is  a  compound  of  primary  coloured  rays  of  different 
■wave  lengths.  Hence  all  the  interference  stripes,  except  the  exactly 
central  ones,  are  formed  by  the  concurrence  of  rays  having  gone 
through  more  or  less  different  lengths  of  route,  and  consequently  with 
a  Mant  of  exact  concurrence  for  the  different  primary  rays,  which 
will  be  greater,  as  we  recede  more  from  the  central  point;  in  other 
words,  the  stripes  towards  each  side  become  more  and  more  coloured, 
and  superimposed,  till  beyond  certain  limits  the  stripes  disappear, 
and  the  whole  mixed  light  is  sensibly  white. 

Now,  if  owing  to  any  cause  one  of  the  two  interfering  rays  were 
retarded  in  its  course  behind  the  other,  the  two  rays  would  not  con- 
cur under  the  same  conditions  of  eqxial  route,  as  before,  at  the  central 
point,  but  it  would  not  be  until  at  some  distance  towards  the  side  on 
which  the  retardation  took  place,  that  they  would  be,  as  it  were, 
placed  on  equal  terms  to  make  up  for  the  retardation  in  the  one  by 
greater  length  of  route  in  the  other;  the  central  point  of  the  stripes, 
and  therefore  the  whole  system  with  it,  would  thus  be  shifted  towards 
that  side.     This  may  be  more  cleai-ly  illustrated  as  follows:    Let 

Fig.  1.  Fig.  2. 

10' 


210  FRKSNET.. 

rays  respectively  pass.  By  making  the  thickness  of 
such  media  vary  gradually,  the  rays  which  traverse  them 
may  still  destroy  or  reinforce  each  other,  just  as  if  they 
had  traversed  routes  perfectly  equal. 

It  hardly  ever  happens  that  any  part  of  space  receives 
direct  light  alone  ;  a  hundred  rays  from  the  same  origin 
arrive  at  that  point  after  reflections  or  refractions  more 
or  less  oblique.     Now,  after  what  has  been  said,  we  may 

two  rays  oo'  interfere,  as  in  fg.  1,  arriving  simultaneously  by  an 
equal  number  of  undulations  respectively,  at  «  and  m',  and  thus  giv- 
ing rise  to  a  light  stripe  at  the  centre  of  the  screen  s,  which  corre- 
sponds to  the  point  of  concurrence  for  equal  routes,  or  when  the  dif- 
ferences for  the  diflerent  colours  are  insensible.  But  now,  as  in.^^r.  2, 
let  the  ray  o  be  intercepted  by  a  glass  screen  g,  by  which  its  undula- 
tions are  retarded.  When  o'  has,  as  before,  arrived  at  u,,  o  will  be  at 
M,  several  undulations  behind  it:  and  the  point  of  concurrence  of  m 
with  u,,  will  not  be  the  same  for  different  colours,  and  the  central  stripe, 
or  point  of  concurrence  for  equal  equivalent  routes,  will  be  that  with 
some  after  wave  u,,  or  will  be  at  -\-  at  some  distance  from  c  towards 
G,  or  the  whole  body  of  stripes  will  be  shifted  towards  the  side  on 
which  G  is  placed. 

This  was  accordingly  exactly  what  Arago  found  to  take  place  when 
he  placed  in  the  path  of  the  light  on  one  side  a  transparenl  screen. 
The  process  by  which  it  is  effected  is  most  clearly  seen  by  intercept- 
ing the  two  rays  with  two  plates  of  glass  of  exactly  the  same  thick- 
ness; and  causing  one  of  them  to  incline  very  slightly,  so  that  the  ray 
on  that  side  passes  through  a  slightly  greater  effective  thickness,  or  is 
a  very  little  retarded;  the  stripes  are  then  seen  to  shift  towards  that 
side,  until  on  increasing  the  inclination,  they  disappear  altogether. 

So  delicate  are  the  indications  aflbrded  by  this  experiment,  and  so 
perfect  the  accordance  between  the  degree  of  shifting  of  the  fringes, 
and  the  refractive  jMwer  of  the  intercepting  medium,  that  Arago  and 
Fresnel  saw  the  advantage  of  employing  it  for  the  inverse  problem  of 
determining  the  most  minute  differences  of  refractive  power,  espe- 
cially those  of  gases  and  vapours,  for  which  no  other  method  could 
be  made  sufficiently  sensible.  To  demonstrate  at  once  the  fact,  and 
the  law  that  this  retardation  is  exactly  in  proportion  to  the  refractive 
power  of  the  glass,  the  translator  long  ago  adopted  a  simple  modifica- 
tion of  this  experiment,  for  an  account  of  which  the  reader  is  referred 
to  the  Fhilos.  May.,  January,  \%Z%.— Translator. 


INTERFERENCE    OP    POLARIZED    LIGHT.  211 

conceive  to  how  many  phenomena  these  repeated  cross- 
ings of  light  may  give  rise  ;  and  how  superfluous  it 
would  have  been  to  seek  the  reason  of  them  as  long  as 
the  laws  of  interference  were  unknown.  Let  us  only 
remark  that  nothing  as  yet  has  indicated  whether  these 
laws  be  equally  applicable  when,  before  the  rays  mix, 
they  have  received  that  modification  of  which  I  have 
already  spoken,  and  which  is  designated  by  the  name  of 
poJarizatton. 

This  question  was  important ;  it  formed  the  object  of 
a  difficult  investigation,  which  Fresnel  undertook  in  con- 
junction with  one  of  his  friends  (Arago).  The  example 
which  they  have  set  in  publishing  their  researches,  of 
distinguishing  which  portion  each  of  them  contributed,  if 
not  with  respect  to  the  material  execution  of  the  differ- 
ent experiments,  at  least  to  the  invention  of  them,  de- 
serves, 1  think,  to  be  followed.  For  associations  of  this 
kind  often  produce  mischief,  because  the  public  persist- 
ing, often  through  blind  caprice,  in  not  treating  the  par- 
ties concerned  on  a  footing  of  perfect  equality,  may 
improperly  excite  the  self-love  of  an  author  ; — perhaps  of 
all  human  passions  that  which  requires  the  most  control. 

Let  us  look  at  the  results  of  the  researches  in  ques- 
tion, as,  without  reference  to  the  important  consequences 
which  have  been  deduced  from  them,  they  deserve  to  be 
stated,  were  it  only  on  account  of  their  intrinsic  singu- 
larity. 

Two  rays  which  are  made  to  change  directly  from  the 
state  of  common  light  to  that  of  rays  polarized  in  the 
same  direction,  preserve,  after  having  received  that  modi- 
fication, the  property  of  interfering  as  before  ;  they  rein- 
force or  destroy  each  other  as  ordinary  rays  do,  and 
under  the   same    conditions.     Two    rays  which    change 


212  FRESNEL. 

directly  from  the  natural  state  to  that  of  rays  polarized 
at  right  angles  to  each  other,  lose  altogether  the  prop- 
erty of  interfering  ;  let  them  be  modified  afterwards  as 
to  the  routes  they  pursue  in  a  thousand  ways,  or  as  to 
the  nature  and  thicknesses  of  the  media  they  traverse ; 
or  even  more,  let  them  be  brought  back  by  suitable  re- 
flexions to  the  condition  of  parallel  polarization  ;  nothing 
of  this  kind  can  give  them  again  the  property  of  being 
able  to  destroy  each  other. 

But  if  two  rays  already  polai'ized  in  directions  at  right 
angles  to  each  other,  and  which  in  consequence  cannot 
act  one  on  the  other,  have  then  received  jjarallel  polar- 
ization, in  passing  out  of  their  natural  state,  it  will  suffice, 
in  order  that  they  again  acquire  the  power  of  inter- 
ference, to  cause  them  to  resume  the  kind  of  polarization 
which  they  originally  possessed.* 

*  The  question  as  to  the  nature  and  modifications  of  the  vibrations 
■whose  aggregate  in  their  different  stages,  or  phases,  constitutes  a 
wave,  may  require  a  word  or  two  of  illustration. 

In  the  first  instance,  in  the  conception  of  waves,  those  who  pursued 
such  a  theory  generallj-  adopted  the  idea  that  the  tethereal  molecules 
oscillated  backwards  and  forwards  in  the  line  of  the  ray;  thej'  could 
not  admit  the  idea  of  their  oscillating  in  any  other  direction.  Yet, 
oscillations  in  any  direction  occurring  in  regular  succession,  might 
constitute  a  wave. 

The  difficulty,  when  more  fully  examined,  had  reference  to  the 
determination  on  admitted  dynamical  principles  of  the  mode  in  which 
the  force  propagating  the  ray  and  acting  in  its  direction  could  give 
rise  to  lateral  disturbance.  Yet  it  is  easy  to  admit,  as  a  rough  illus- 
tration, the  case  of  a  rope  fastened  at  one  end  and  agitated  at  the 
other  by  the  hand;  when  we  can  easily  cause  a  series  of  waves  to 
run  along  it;  but  the  particles  of  the  rope  really  retain  their  original 
distances  from  the  hand,  and  merely  move  up  and  down  in  directions 
transverse  to  its  length.  In  a  somewhat  similar  way,  the  EBthereal 
molecules  are,  according  to  this  theory,  made  to  vibrate,  or  as  Fres- 
nel  afterwards  graphically  expressed  it,  to  "  tremble  laterally." 

At  length.  Young  began  to  entertain  the  idea  tliat  the  molecules 


GENERAL    THEOKY.  213 

It  is  impossible  not  to  feel  astonishment,  when  we  for 
the  first  time  learn  that  two  rays  of  light  can  mutually 

might  oscillate  in  parallel  directions  transverse  to  the  direction  of  the 
ray;  though  he  thought  that  the  longitudinal  vibrations  might  exist 
also.  But  he  long  hesitated  to  adopt  such  an  idea,  regarding  it  as 
inexplicable  on  any  dynamical  principles.  Fresnel  independently 
started  the  same  idea  of  transverse  vibrations,  alone;  but  he  was 
equally  reluctant  to  propose  it,  on  the  ground  of  a  similar  mechanical 
difficulty;  yet  he  distinctly  acknowledged  Young's  priority  in  the 
announcement  of  the  general  idea.  "  M.  Young,"  he  says,  "  more 
bold  in  his  conjectures  and  less  confiding  in  the  views  of  geometers, 
published  it  before  me,  though  perhaps  he  thought  of  it  after  me." 
And  on  the  same  point,  Dr.  Whewell  mentions  from  personal  infor- 
mation, that  "  Arago  was  wont  to  relate  that  when  he  and  Fresnel 
had  obtained  their  joint  experimental  results  of  the  non-interference 
of  oppositely  polarized  pencils,  and  that  when  Fresnel  had  pointed 
out  that  transverse  vibrations  were  the  only  possible  translation  of 
this  fixct  into  the  undulatory  theory,  he  himself  protested  that  he  had 
not  the  courage  to  publish  such  a  conception;  and,  accordingly,  the 
second  part  of  the  memoir  was  published  in  Fresnel's  name  alone. 
What  renders  this  more  remarkable  is,  that  it  occurred  when  Arago 
had  in  his  possession  the  very  letter  of  Young  (1818),  in  which  he 
proposed  the  same  suggestion." — Hist,  of  Inductive  Sciences,  ii.  418. 

Fresnel  deduced  transverse  vibrations  on  dynamical  grounds  which 
had  been  open  to  some  degree  of  question.  But  the  nature  of  the 
relation  between  the  partial  differential  equation  which  he  gives,  and 
the  wave  function  which  is  the  solution  of  it,  clearly  involves  no  nec- 
essary restriction  of  the  direction  of  vibration.  That  equation  is  of 
the  same  general  form  as  that  given  b}-  Euler,  as  referring  to  sound. 
Such  an  equation  suffices  for  light  considered  as  homogeneous.  It 
expresses  generally  the  relation  of  particles  in  motion,  such  that 
if  the  time  and  the  position  of  the  particles  be  increased  by  corre- 
sponding changes,  the  form  of  the  function  will  be  unaltered,  or  the 
motions  recur  periodically,  which  constitutes  the  essential  idea  of  a 
wave.    Its  fonn  is  generally 

d^u  d-u 

'dfi~  ~  ^  d^ 
where  t  is  the  time,  x,  the  distance  along  a  given  axis,  and  m,  the  dis- 
placement corresponding  to  the  time,  < ;  c,  a  constant.     The  solution 
of  this  equation  is  easily  seen  to  be  the  wave  function. 
u  =  sin  {nt  —  hx) 


214  fresnp:!.. 

destroy  each   other,  that  darkness  may  result  from  the 
superposition  of  two  portions  of  light.     But  when  this 

Since,  if  we  take  the  partial  difierentials  in  i-espect  to  i  and  to  x, 

du  ,  du        ^  , 

-^  =  w  cos  int  —  kx)  -T-  =^  k  cos  int  —  kx) 

dt  dx 

—  =  —  vP'U  ■ —  ^^=  —  li^u 

dt^  dx-2 

Whence,  c?%  n''^  d^u 

dl^  "  ~  W  dx^ 
And  since  that  wave-function  goes  through  all  its  changes  while  t, 
increases  to  —  and  the  velocity  f  =  -r-  the   time  of  the  undulation 


_27r 

1 

In 

T 

n 

and 

V 

— 

T 

— 

•Zn 

Whence,  n  = and  A;  =  — 

Or  the  formula  becomes  (adopting  an  arbitrary  coefficient,  a,  for 
the  amplitude  of  vibration  which  is  wholly  independent  of  the  other 
quantities) 

277 

M  =  a  sin  -r-  {vt  —  x). 

A 

n 
Here  it  is  to  be  observed,  all  depends  on  the  coefScient-r  being 

constant.  To  obtain  a  similar  equation  with  a  variable  velocity  or 
refraction  is  the  object  of  the  researches  of  M.  Cauchy. 

The  more  extended  views  of  M.  Cauchy  have  led  to  the  deduction 
of  analogous,  but  more  complex,  equations,  exhibiting  resulting  ex- 
pressions for  the  displacement,  in  three  rectangular  directions;  besides 
including  in  the  analysis  a  coefficient  which  expresses  the  variable 
relation  of  the  velocity  which  gives  the  theoretical  explanation  of  un- 
equal refrangibility.  These  forms  thus  include  the  deduction  of 
transverse  vibrations,  as  a  direct  consequence  of  the  first  assump- 
tions, as  to  the  constitution  of  an  sBthereal  medium.  But,  with  refer- 
ence to  light,  considered  as  homogeneous,  the  conditions  admit  of 
great  simplification;  which  is  best  shown  in  that  form  of  the  investi- 
gation which  was  pursued  by  Sir  J.  Lubbock  (Pliibs.  Mag.  Nov. 
1837),  where,  if  the  fourth  powers  of  the  disturbed  distances  of  the 
molecules  are  neglected,  the  equations  are  at  once  reduced  to  the 
form  above. 

The  object  of  M.  Cauchy's  researches  here  alluded  to  was  to  ex- 


THEORY    OF    INTERFERENCE.  215 

property  of  the  rays  has  been  once  established,  is  it  not 
still  more  exti-aordinary  that  we  can  deprive  them  of  it? 

plain  the  unequal  refrangibility  of  light.  To  give  some  general  notion 
of  the  nature  of  the  subject,  we  may  here  briefly  observe,  that  in  the 
explanation  of  refraction  before  given,  [Life  of  Malus,  note,]  it  is 
clear  that  as  the  inclination  of  the  common  tangent  to  the  contempo- 
nincous  circular  waves  determines  the  refraction,  this  depends  on  the 
diminution  of  the  wave  length  within  the  denser  medium;  and  if  this 
inclination  be  deteniiined  for  a  ray  of  any  given  wave  length,  then  for 
another  whose  wave  length  within  the  medium  is  different,  and  in  a 
given  ratio  to  the  former,  the  radii  of  the  contemporaneous  waves  will 
be  in  the  same  ratio  as  the  former,  or  their  difference  from  the  former 
will  be  in  the  same  ratio,  consequentlj'  the  common  tangent  of  these 
second  circles  will  not  be  parallel  to  the  first,  but  inclined  at  a  differ- 
ent angle:  or  the  angle  of  refraction  will  be  different.  Thus  if  for 
any  particular  [primary  ra}^  the  wave  length  within  the  medium  be 

X 
Til  ^        that  of  the  incident  ray  being  /I  and  u  the  index  for  that 
i«y  -^  '^ 

rav,  /I  =  6  sin  i. 

1 
then  2,1  =  h  sin  r  =  ~ 

or  in  other  words,  the  refraction  will  be  different  from  each  primary 
ray.  But  //,  and  a,  do.  not  follow  any  simple  ratio.  The  more  com- 
plex expression  on  which  that  relation  depends,  is  the  result  of  M. 
Cauchy's  theory,  viz: — 

[See  Professor  Powell's  Treatise  on  the  Undulatory  Theory,  sect. 
vi.] 

Experimentally,  the  transverse  vibrations  receive  their  main  sup- 
port from  the  analysis  of  the  coloured  tints,  developed  in  polarized 
light  by  the  interposition  of  plates  of  crystal  (such  as  those  of  mica, 
selenite,  &c.),  when  examined  by  an  analj'zer. 

Young  ascribed  these  colours  generally  to  interference ;  but  both 
Fresnel  and  Arago  pointed  out  that  this  explanation  was  incomplete. 
Why  did  it  only  take  place  in  polarized  light,  and  even  then  not  until 
the  analyzer  had  been  applied?  These  questions  could  not  be  an- 
swered till  another  law  had  been  discovered;  as  it  soon  after  was,  by 
the  joint  labours  of  those  two  philosophers. 

It  was  clear  that  in  polarization  all  the  vibrations  were  performed 
in  one  and  the  same  plane,  in  whatever  direction  they  might  be  exe- 


216 


tliat  a  given  ray  loses  it  momentarily,  and  that  another 
given  ray,  on  the  contrary,  is  deprived  of  it  for  ever  ? 
The  theory  of  interferences,  considered  in  this  point  of 
view,  seems  more  like  the  reveries  of  a  disordered  brain, 
than  the  exact,  inevitable  consequence  of  numberless 
experiments,  clear  of  all  possible  objection.     And  fur- 

cuted.  But  it  was  not  until  after  lengthened  investigation  that  the 
two  philosophers  just  named  succeeded  in  establishing  experimen- 
tally the  important  law  (obvious  as  it  now  seems,)  that  ^^  polarized  rays 
can  only  interfere  iclien  they  are  polarized  in  the  same  plane.''''  If  they 
were  polai'ized  in  rectangular  planes  (for  example),  no  interference 
could  result,  were  all  other  conditions  ever  so  perfectly  fulfilled.  Now, 
this  could  only  be  explained  on  the  supposition  of  the  vibrations 
being  performed  in  planes  transverse  to  the  ray.  Granting  that  in  a 
ray  polarized  in  one  plane  all  the  vibrations  take  place  in  one  plane, 
(whether  in  the  same  plane  or  perpendicular  to  it,)  it  is  then  readily 
seen  that  when  the  vibrations  of  two  raj's  are  at  right  angles  to  each 
other,  there  can  be  no  mutual  destruction,  or  mutual  cooperation.  It 
is  only  when  they  are  in  the  same  plane  that  this  can  occur. 

This  principle  was  at  length  found  to  supply  the  explanation  of  the 
polarized  tints.    Every  ray  of  the  light  (p)  originally  polarized  iu  one 


plane,  in  traversing  the  crystal  plate  (c)  was  divided  into  two;  an 
ordinary  (o)  and  an  extraordinary  (e);  all  those  of  the  one  kind,  o,  o^, 
o",  &c.  being  polarized  in  one  plane,  and  all  of  the  other,  e,  c',  e'',  &c., 
in  a  plane  at  right  angles  to  the  last.  But  in  each  ray  o,  and  e,  di- 
verge from  each  other  by  a  very  small  angle.  The  whole  pencil  also 
diverges  at  a  small  angle  from  p;  thus,  the  only  rays  which  can  coin- 
cide in  direction,  will  be  a  ray  o,  of  one  set,  with  a  ray  e'  of  the  next; 
— (/,  with  e",  &c.  &c.,  and  as  these  are  unequallj'  retarded  in  differ- 
ent degrees  according  to  their  inclination,  they  would  be  in  a  con- 
dition to  give  interference,  were  it  not  that  being  polarized  in  places 


POLARIZATION.  217 

ther,  it  is  not  only  on  account  of  its  singularity  that  this 
theory  ought  to  command  the  attention  of  the  physicist ; 
Fresnel  found  it  the  key  to  all  the  beautiful  phenomena 
of  colours,  which  are  produced  in  plates  of  crystal  pos- 
sessing double  refraction  ;  he  analyzed  them  in  all  their 
details ;  he  determined  their  most  hidden  laws ;  he 
proved  that  they  were  only  particular  cases  of  inter- 
ferences. He  thus  overturned  from  their  base  many 
scientific  romances  to  which  these  phenomena  had  given 
birth,  and  which  had  secured  more  than  one  pros- 
elyte, whether  by  their  striking  nature  or  the  distin- 
guished merit  of  their  authors.  In  a  word,  here,  as  in 
every  branch  of  science  which  is  advancing  towards  per- 
fection, the  facts  have  seemed  complicated  only  because 
we  examined  them  at  too  near  a  distance  and  with  too 
microscopic  a  view  ;  but  at  the  same  time,  by  a  more 
enlarged  conception,  their  causes  have  been  found  to  be 
more  simple  than  we  might  have  expected. 

rOLARIZATION. 

Although  I  am  aware  at  what  point  we  risk  tiring  even 
the  most  kindly  disposed  audience  when  we  speak  long 

at  rif/lil  angles  to  each  other  they  could  not.  It  only  required  then 
the  action  of  the  analyzer  (a)  to  resolve  each  vibration  again  into 


two,  at  right  angles,  of  which  two  sets  in  a  plane  perpendicular  to 
that  of  analyzation  are  suppressed;  and  two  in  that  plane  transmit- 
ted; and  which.,  consequently,  being  in  parallel  planes,  are  able  to 
give  interference,  and  produce  the  observed  coloured  tints. 

8KC.  SEK.  10 


218  FRESNEL. 

on  the  same  subject,  I  find  myself  still  carried  back,  by 
the  nature  of  Fresnel's  labours,  to  the  subject  of  double 
refraction:  but,  this  time,  instead  cf  occupying  myself 
with  the  manner  in  which  the  rays  divide  in  passing 
throu'i^h  certain  crystals,  I  will  examine  the  permanent 
modifications  which  they  receive  :  I  will  present,  in  one 
word,  the  principal  features  of  the  new  branch  of  optics 
which  bears  the  name  of  polarization  ofUrjht. 

Every  ray  of  light  falling  even  perpendicularly  on  any 
surface,  natural  or  artificial,  of  the  transparent  crystals  of 
carbonate  of  lime,  called  also  calc  spar,  or  Iceland  spar, 
is  divided  into  two.  One  portion  passes  tlirough  the 
crystal  without  deviation,  which  we  call  the  ordinary  I'ay ; 
the  other  undergoes  a  sensible  refraction,  and  for  that 
reason  has  very  justly  the  name  of  the  extraordinary  ray. 
Both  the  ordinary  and  extraordinary  i-ay  lie  in  one  plane 
perpendicular  to  the  face  of  the  crystal.  The  considera- 
tion of  this  plane  is  important,  for  it  is  this  which  deter- 
mines the  direction  Avhich  the  extraordinary  ray  will 
take ;  and  in  consequence  a  special  name  has  been  given 
to  it,  "  the  principal  section." 

These  points  being  premised,  I  will  suppose,  to  fix  the 
ideas,  that  a  particular  crystal  of  calc  spar  has  its  princi- 
pal section  directed  north  and  south.  Below  this,  and  at 
any  distance,  we  will  place  another  similar  crystal  turned 
similarly  ;  that  is,  so  th.at  its  principal  section  shall  also 
lie  in  the  meridian.  What  will  result  from  this  disposi- 
tion, if  light  traverse  the  whole  system  ?  A  single  ray 
impinges  on  the  first  crystal  but  it  emerges  in  two  rays : 
each  of  these  again  seems  as  if  it  should  undergo  a  double 
refraction  in  the  second  crystal  ;  and  thence  we  might 
expect  four  emergent  rays.  Yet  this  does  not  happen. 
The  rays  emanating  from  the  first  crystal  are  not  divided 


DOUBLE    REFRACTION.  219 

again  by  the  second.  The  ordinary  ray  remains  an  ordi- 
nary ray,  and  the  extraordinary  undergoes  solely  an 
extraordinary  refraction.  Thus,  in  traversing  the  first 
crystal,  the  luminous  rays  have  changed  their  nature ; 
they  have  lost  one  of  their  former  characteristics,  that  of 
constantly  undergoing  double  refraction  in  traversing  Ice- 
land crystal.* 

It  is  necessary  that  we  should  fully  bear  in  mind  what 
rays  of  light  are,  and  then,  perhaps,  we  shall  admit  that 
an  experiment,  by  the  aid  of  which  they  change  their 
original  properties  in  so  manifest  a  way,  deserves  to  be 
known  even  by«those  to  whom  science  is  merely  an  object 
of  curiosity. 

The  idea  which  in  the  first  instance  presents  itself  to 
the  mind,  when  we  wish  to  explain  this  singular  result  of 
which  I  have  just  given  an  account,  consists  in  supposing 
that  in  every  ray  there  might  exist  two  distinct  species  of 
molecules :  that  the  one  species  must  always  undergo  the 
ordinary  refraction ;  the  other,  the  extraordinary  alone. 
But  a  very  simple  experiment  upsets  this  hypothesis  en- 
tirely. In  fact,  when  the  principal  section  of  the  second 
crystal,  instead  of  being  directed  north  and  south  as  above 
supposed,  is  pointed  east  and  west,  the  ray  which  was  the 
ordinary  ray  in  the  first  crystal,  becomes  the  extraordi- 
nary in  the  second  ;  and  reciprocally. 

What,  then,  is  there  different  in  reality  between  the 
two  experiments  which  give  results  so  dissimilar  ?  There 
is  one  circumstance,  very  simple,  and  full  of  import  at 
first  sight :  it  is,  that  at  first  the  principal  section  of  the 
second  crystal  cuts  the  rays  coming  from  the  first  through 
their  north  and  south  sides,  and  in  the  second  case,  through 
their  east  and  west  sides. 

*  For  illustration  of  this  subject,  see  note  to  the  Life  of  Malus. 


220  FKESNEL. 

There  must  be  then,  in  each  of  these  rays,  north  and 
south  sides  in  some  way  different  from  their  east  and 
west  sides.  And  further,  tlie  north  and  south  sides  of 
the  ordinary  ray  ouglit  to  have  precisely  the  same  prop- 
erties as  the  east  and  west  sides  of  the  extraordinary  ray  ; 
so  that  if  this  hist  ray  make  a  quarter  of  a  circuit  about 
tlie  hne  of  its  length  it  will  be  impossible  to  distinguish 
one  from  the  other.  The  rays  of  light  are  so  subtle  that 
thousands  of  millions  of  these  rays  can  pass  simultane- 
ously through  the  eye  of  a  needle  without  interfering  : 
yet  we  find  ourselves  obliged  to  take  into  account  the 
idea  of  their  sides,  and  to  recognize,  on  their  opposite 
sides,  dissimila7'  properties. 

When  speaking  of  a  magnet,  natural  or  artificial  phys- 
icists affirm  it  to  have  poles.  They  mean  only  that  cer- 
tain points  on  its  surface  are  found  endowed  with  certain 
properties  which  are  not  found,  or  at  least  only  show 
themselves  feebly,  at  any  other  points.  We  have,  then, 
equal  reason  to  say  the  same  thing  of  the  ordinary  and 
extraordinary  rays  of  light  which  proceed  from  the  divis- 
ion of  the  beam  which  passes  through  Iceland  spar ;  and 
in  contradistinction  to  the  natural  rays  in  which  all  points 
appear  alike,  we  may  rightly  call  them  polarized  rays. 

In  order,  however,  that  we  may  not  extend  beyond  its 
proper  limits  the  analogy  of  a  polarized  ray  and  a  mag- 
net, it  is  important  to  remark  well  that  in  the  ray,  the 
poles  diametrically  opposite  appear  to  possess  exactly  the 
same  properties  ;  whilst  the  dissimilar  poles  are  situated 
on  sides  of  the  ray  whose  positions  are  at  right  angles  to 
each  other. 

The  lines  resembling  diameters,  which  join  the  similar 
poles,  in  every  ray  deserve  particular  attention.  When- 
ever, in  two  distinct  rays,  these  lines  are  parallel,  we  say 


DOUBLE    REFRACTION.  221 

that  the  rays  are  polarized  in  the  same  plane.  There  is, 
consequently,  no  need  to  add  that  two  rays  polarized  at 
right  angles  to  each  other  must  have  their  similar  poles 
in  two  directions  perpendicular  the  one  to  the  other. 

The  two  rays,  the  ordinary  and  the  extraordinary  for 
example,  given  by  any  ci-ystal  are  always  polarized  at 
right  angles  to  each  other. 

All  that  I  have  just  said  of  polarization  of  light  was 
recognized  by  Huyghens  and  Newton  before  the  end  of 
the  17th  century;  and  never,  certainly,  had  a  more  curi- 
ous subject  for  research  been  offered  to  the  meditations 
of  experimenters.  Nevertheless,  we  must  pass  over  an 
interval  of  a  century  after  that  pei-iod  before  we  find,  I 
do  not  say  any  fresh  discoveries,  but  even  any  more 
reseai'ches  for  the  object  of  carrying  out  this  branch  of 
optics. 

The  history  of  all  sciences  presents  a  multitude  of  sin- 
gular incidents  of  a  similar  kind.  In  the  progress  of 
each  science  there  occur  periodically  certain  epochs  when, 
after  great  efforts,  men  usually  suppose  themselves  to 
have  arrived  at  a  limit  in  their  advance.  Then  expei'i- 
raenters  are  in  general  timid  ;  they  fancy  themselves 
chargeable  with  a  want  of  modesty,  with  a  sort  of  profa- 
nation, if  they  dare  to  lay  an  indiscreet  hand  on  the  bar- 
riers which  their  illustrious  predecessors  have  erected ; 
and  thus  they  generally  content  themselves  with  perfect- 
ing the  numerical  elements,  or  filling  up  some  deficien- 
cies, bestowing  on  the  inquiry  a  labour  often  arduous, 
and  which  yet  scarcely  attracts  any  notice  from  the 
world. 

In  a  word,  the  experiments  of  Huyghens  had  clearly 
established  the  fact  that  double  refraction  modifies  the 
original  properties  of  light  in  such  a  manner  that,  after 


222  FRESNEL. 

having  once  undergone  this  modification,  the  rays  remain 
single,  or  again  subdivide  into  two,  according  to  the  direc- 
tion in  which  they  fall  upon  a  second  crystal  presented  to 
them.  But  do  these  modifications  show  a  relation  exclu- 
sively to  double  refraction  ?  do  all  their  other  properties 
remain  uninfluenced  ? 

It  was  from  the  labours  of  one  of  our  most  distinguished 
colleagues  (like  Fresnel,  early  snatched  away  from  the 
sciences  of  which  he  was  the  hope)  that  we  have  been 
enabled  to  answer  these  important  questions.  Malus  dis- 
covered, in  fact,  that,  in  the  act  of  reflexion,  polarized 
rays  are  differently  affected  from  common  rays  :  the  lat- 
ter, as  every  one  knows,  are  partially  reflected  when  they 
fall  even  on  transparent  bodies,  whatever  may  be  the 
angle  of  incidence,  and  whatever  the  position  of  the  re- 
flecting surface  with  respect  to  the  sides  of  the  ray. 
When,  on  the  contrary,  the  case  is  one  of  polarized  light, 
there  is  always  one  situation  of  the  reflecting  surface, 
relatively  to  the  poles,  or  sides,  in  which  all  reflexion 
disappears  if  in  this  situation  the  reflexion  take  at  a 
particular  incidence,  which  is  different  for  each  reflecting 
surface,  according  to  the  nature  of  the  substance  of  which 
it  is  foi'med. 

If,  after  this  curious  observation,  double  refraction 
ceased  to  be  the  07ili/  means  of  distinguishing  polarized 
from  common  light,  at  least  it  seemed  to  be  the  only  way 
by  which  rays  of  light  could  become  polarized.  But 
soon  a  new  experiment  of  Malus  taught  the  scientific 
world,  to  its  great  surprise,  that  there  existed  other 
methods,  far  less  abstruse,  for  producing  this  modifica- 
tion. The  most  simple  phenomenon  of  optics,  the  re- 
flexion of  light  from  a  transparent  mirror,  is  a  powerful 
means  of  producing  polarization.      Light,  which  is  re- 


PLANE    POLARIZATION.  223 

fleeted  at  the  surface  of  water  at  an  angle  of  37°,  or 
from  the  surface  of  glass  at  an  inclination  of  35°  25',  is 
as  completely  polarized  as  the  two  rays,  ordinary  and 
extraordinary,  proceeding  from  a  crystal  of  Iceland  spar. 

The  reflexion  of  light  long  ago  occupied  observers  in 
the  age  of  Plato  and  of  Euclid  :  since  that  epoch  it  had 
been  the  object  of  thousands  of  experiments,  of  hundreds 
of  theoretical  speculations  ;  the  law  according  to  which  it 
proceeds  serves  as  the  basis  of  a  great  number  of  instru- 
ments, ancient  and  modern.  Among  the  multitude  of 
enlightened  minds,  of  men  of  genius,  of  skilful  artists, 
who,  during  more  than  2300  years,  have  been  occupied 
with  this  phenomenon,  no  one  ever  aimed  at  any  other 
object  than  the  means  of  making  tlie  rays  divide,  or  of 
causing  them  to  diverge  or  converge  ;  no  one  ever  imag- 
ined that  reflected  light  ought  not  to  possess  all  the  same 
properties  as  the  incident  light,  or  that  a  change  of  path 
would  be  the  cause  of  a  change  of  nature.  Generations 
of  observers  thus  succeeded  each  other  during  several 
thousands  of  years,  every  day  toucliing  closely  on  the 
most  beautiful  discoveries  without  actually  making  them. 

Malus,  as  I  have  already  explained,  gave  a  means  of 
polarizing  light  different  from  that  which  Huyghens  had 
formerly  announced.  But  the  polarizations  produced  by 
the  two  methods  Avere  identically  the  same.  The  re- 
flected rays  and  those  which  proceed  out  of  an  Iceland 
crystal  possess  exactly  the  same  properties.  Since  that 
time  a  member  of  this  Academy  (Arago)  has  discovered 
a  kind  of  polarization*  entirely  distinct,  and  which  mani- 

*  It  maj'  be  necessary  for  some  readers  to  explain  that,  in  this  some- 
■what  paradoxical  mode  of  speaking,  the  autlior  is  referring  to  his  own 
discoverj'  of  the  polarized  tints;  and  his  meaning  is  simply  that  if,  in 
polarized  light,  there  be  placed  a  thin  film,  e.  g.,  of  selenite  or  mica, 
and  it  be  viewed  through  a  doubly  refracting  crystal  as  an  analj^zer, 


224  FRESNEL. 

fests  itself  in  a  different  way  from  that  of  difference  of 
intensity.  The  rays  subjected  to  it,  for  example,  always 
give  two  images  in  traversing  calc  spar ;  but  these  images 
are  each  entirely  tinted  with  a  bright  and  uniform  colour. 
Thus,  though  the  incident  light  may  be  white,  the  ordi- 
nary ray  may  be  entirely  red,  orange,  yellow,  green,  blue, 
or  violet,  according  to  the  direction  in  which  the  prin- 
cipal section  of  the  crystal  cuts  the  ray  :  and  as  to  the 
extraordinary  ray,  it  will  not  suffice  to  say  that  it  never 
resembles  the  ordinary ;  we  must  say  that  it  differs  from 
it  as  widely  as  possible ;  that  if  the  one,  for  example,  is 
coloured  red,  the  other  shows  a  bright  green,  and  so  on 
for  the  rest  of  the  prismatic  tints. 

"When  this  new  kind  of  polarized  rays  are  reflected 
from  a  transparent  mirror,  we  perceive  otiier  phenomena 
not  less  curious.  Let  us  conceive,  in  fact,  to  fix  the  ideas, 
that  one  of  these  rays  be  vertical,  and  that  it  fall  on  a  re- 
flector of  pure  glass  at  an  angle  of  about  35°,  this  mirror 
may  be  on  the  right  side  of  the  ray  :  and  the  inclination 
remaining  constant,  it  may  be  turned  to  its  left,  before  it, 
or  behind  it,  or  in  any  intermediate  position.  We  may 
remember  that  the  incident  ray  was  white  ;  then,  in  any 
of  these  positions  of  the  glass  reflector,  the  ray  will  not 
have  this  colour :  it  will  be  now  red,  now  orange,  yellow, 
green,  blue,  indigo,  violet,  according  to  the  side  on  which 
the  glass  presents  itself  to  the  incident  ray  ;  it  is,  in  fact, 
precisely  in  this  order  that  the  tints  succeed  one  another, 

both  the  images  will  be  coloured,  and  their  tints  complementary.  The 
originally  polarized  light  is  divided  again  into  two  oppositely  polarized 
pencils  in  passing  through  the  film,  or  as  Professor  J.  Forbes  has  termed 
it,  Dipohirized;  others  had  termed  it  \>Kpolarized.  This  is  what  Arago 
here  calls  a  new  and  entirely  distinct  kind  of  polarization;  though  the 
term  is,  perhaps,  not  very  happily  applied.  This  is  what  was  explained 
at  large  in  a  previous  note. 


CHROMATIC    POLARIZATION.  225 

as  we  gradually  make  the  mirror  go  through  all  possible 
changes  of  position,  Here  there  ai'e  not  only  four  poles 
placed  in  two  rectangular  directions,  which  we  must  ad- 
mit in  the  constitution  of  the  ray,  but  we  see  that  there 
are  thousands  ;  that  every  point  in  the  circumference 
round  the  ray  has  a  special  character ;  that  every  face 
which  it  presents  produces  in  the  reflexion  a  particular 
tint.  This  strange  dislocation  of  the  natural  ray  (I  may 
be  allowed  this  word,  sjnce  it  exactly  expresses  the  fact) 
thus  affords  the  means  of  decomjoosing  white  light  by 
means  of  reflexion.  The  colours,  it  must  be  avowed, 
have  not  all  the  homogeneity  of  those  which  Newton  ob- 
tained by  the  prism ;  but  also  the  object  from  which  they 
originate  does  not  undergo  any  distortion,  as  in  prismatic 
refraction :  and  in  a  multitude  of  researches  this  is  a  point 
of  material  importance. 

To  discover  whether  a  ray  has  received  the  polariza- 
tion of  Huyghens  and  Malus,  or  that  of  which  I  have 
just  spoken,  and  which  wc  call  chromatic  polarization,  it 
suffices  as  we  have  seen,  to  make  it  undergo  double  re- 
fraction :  but  from  the  fact  that  a  ray  in  traversing  a 
crystal  of  Iceland  spar  always  gives  two  images  of  white 
light  and  of  equal  intensity,  it  will  not  follow  that  it  is 
formed  originally  of  common  light :  this  is  again  the 
discovery  of  Fresnel.*     It  is  he  who  first  pointed  out 

*  The  author  would  have  expressed  his  meaning  more  clearly  to 
general  apprehension  if  he  had  said,  that  natural  or  unpolarized  white 
light,  on  traversing  Iceland  spar,  gives  two  white  images  in  all  posi- 
tions: an  ordinarily  polarized  ray  does  not;  but  there  is  a  kind  of 
light  which  gives  always  two  images,  and  j^et  is  not  unpolarized :  this 
is  the  circularly  polarized  light,  discovered  by  Fresnel.  One  test 
which  distinguishes  it  from  common  light  is,  that  on  interposing  a 
crystallized  plate  of  seleuite,  mica,  &c.,  before  receiving  the  light  on 
10* 


226  FRESNEL. 

that  a  ray  may  have  the  same  properties  round  all  points 
of  its  circumference,  and  yet  not  be  common  light.  To 
show  by  a  single  example  that  these  two  species  of  light 
comport  themselves  differently,  and  ought  not  to  be  con- 
founded, I  Avill  observe  that,  in  undergoing  double  re- 
fraction, a  natural  ray  after  traversing  a  plate  of  crystal 
gives  two  white  images,  wliile  under  the  same  conditions 
the  ray  of  Fresnel  is  decomposed  into  two  beams,  each 
hrilliantly  coloured. 

This  new  modification,  which,  having  no  reference  to 
the  different  sides  of  a  ray,  has  been  designated  circidar 
polay-ization,  can  be  impressed  upon  rays  ordinarily 
polarized,  by  making  them  undergo  two  successive  total 
reflexions  from  the  internal  surfaces  of  a  piece  of  glass 
suitably  formed.*  The  pleasure  of  having  his  name  as- 
sociated with  a  new  kind  of  polarization  hitherto  unsus- 
pected, would  probably  have  sufficed  for  the  vanity  of 
an  ordinary  experimenter,  and  his  researches  would  not 
have  extended  beyond  that  point.  But  Fresnel  was 
actuated  by  more  elevated  sentiments ;  in  his  eyes 
nothing  seemed  to  have  been  done  while  any  thing  re- 
mained to  do.     He  sought,  therefore,  if  there  were  not 

the  double  refracting  crystal,  the  two  images  in  the  former  case  will 
be  always  white,  in  the  later  coloured. 

*  In  the  instance  mentioned,  Fresnel  showed,  by  a  remarkable  in- 
stance of  theoretical  prediction,  that  a  ray  polarized  at  45°  to  the 
plane  of  incidence,  and  twice  reflected  internally  from  glass,  will 
emerge  in  the  condition  of  two  ra\-s  polarized  in  planes  at  right 
angles,  and  one  retarded  by  one  fourth  of  a  wave-length  behind  the 
other;  these  being  superimposed  will,  by  mathematical  consequence, 
give  rise  to  vibrations,  no  longer  plane,  but  performed  in  circles;  or  in 
ellipses,  if  the  retardation  be  any  other  fraction  of  a  wave-length. 
Such  a  piece  of  glass  is  called  Fresnel's  Rhomb.  The  course  of  the 
ray  will  be  apparent  by  inspection  of  the  annexed  diagram,  which 
needs  no  further  explanation. 


CIRCULAR    POLARIZATION. 


227 


other  means  by  which  to  produce  circular  polarization  ; 
and,  as  usual,  a  remarkable  discovery  was  the  reward  of 
these  efforts.  This  discovery  may  be  announced  in  two 
words  ;  there  is  a  partmdar  kind  of  double  refraction 
which  communicates  to  rays  circular  polarization,  as  the 
double  refraction  of  Iceland  spar  communicates  the  com- 

The  mechanical  conception  of  two  rectilinear  vibrations  at  right 


angles  compounded,  giving  an  elliptical  or  circiilar  vibration,  may  be 
illustrated  by  a  very  simple  contrivance,  which  may  be  described  as 
follows : — 

On  any  convenient  support,  there  projects  an  arm  terminating  in 


22^  FRESNEL. 

mon  polarization  of  Huygliens.  This  special  double  re- 
fraction, results  not  from  the  nature  of  the  crystal,  but 
two  branches,  on  which,  by  the  pivots  g  g',  a  smah  frame  swings.    In 


D  ii 

this  frame,  by  the  pivots  h  h^,  whose  axis  is  at  right  angles  to  g  g',  a 
pendulum  p  vibrates.  (The  upper  end  is  light,  and  carries  a  white 
ball  or  disk,  carried  up  to  such  a  height  as  to  be  conspicuous  for  lec- 
ture illustrations.) 

Now,  by  the  pivots  h  h/  the  pendulum  can  only  vibrate  in  the  plane 
of  c  D,  and  by  the  pivots  o  gi  it  can  only  vibrate  in  the  plane  of  a  b 
at  right  angles  to  c  d.  If  now  motion  be  given  it  in  one  of  these  planes, 
and  at  an  instant  after  in  the  other,  the  result  will  be  a  revolution  in 
the  ellipse  e  e/,  which  will  be  a  circle  if  the  interval  be  exactly  one 
fourth  of  a  vibration. 

Or  mathematically  thus : — 

Let  the  waves  in  planes  at  right  angles,  with  a  difference  of  retarda- 
tion d,  be  expressed  by 

z  =  a  sin  (nt  —  kx)        y  =  13  sin  (nt —  kx  -{-  d) 

Hence,  —  =  sin  (nt  —  kx)  and       /  \ ^2 

"  ■%/  —  =  cos  (n<  —  kx), 

or  expanding  ?/  and  substituting 

Whence  transposing  and  squaring 

-TT,  +  ^  —  ^  cos  rf  =  sin  2(i 
/3^        a2       ap 

The  equation  to  an  ellipse :  which  becomes  a  circle  if  fl  =  /3  and 
d  =  90°.—  Translator. 


CIRCULAR    POLARIZATIOX. 


229 


from  certain  sections  of  it  which  Fresnel  pointed  out. 
The  properties  of  rays  circularlj  polarized  also  led  our 
colleague  to  new  and  very  curious  means  of  producing 
coloured  polarization.* 

*  The  author  must  be  supposed  here  to  allude  to  that  remarkable 
instance  of  circular  polarization  which  is  produced  by  transmitting  a 
plane  polarized  ray  along  the  axis  of  quartz  or  rock  crystal,  and  which 
depends,  as  he  says,  not  on  the  nature  of  the  crystal,  but  on  the  section 
of  it,  that  is  to  say,  on  the  thickness:  the  effect  continually  changing 
as  slices  are  cut  from  the  crystal  perpendicular  to  its  axis  of  increas- 
ing thickness.  This  statement  is  somewhat  remarkable,  as  he  here 
unequivocally  ascribes  the  discovery  to  Fresnel,  which  has  been 
usually  by  English  writers  ascribed  to  himself. 

The  term  "  rotatory  "  polarization  has  been  since  appropriated  to 
describe  this  phenomenon.  Yet  the  student  must  be  careful  to  dis- 
tinguish the  application  of  this  term  from  that  of  "  circular"  polar- 
ization. The  light  is  in  fact  circularly  polarized:  but  the  effect 
called  "rotation"  is  quite  distinct  from  the '•  circularity."  It  may 
be  desirable  to  add  a  brief  explanation.    Let  a  ray,  r,  polarized  in  a 


K 

p 

^ 

\ 

/ 

\ 

230  FRESNEL. 

In  all  times  and  all  countries,  we  find  morose  disposi- 
tions, who,  though  ready  enough  to  proclaim  the  glories 
of  the  dead,  do  not  treat' their  contemporaries  with  any 
thing  like  the  same  favour.  As  soon  as  a  discovery  is 
announced,  they  deny  its  truth  :  they  contest  its  novelty, 
and  pretend  to  detect  it  in  some  passage  of  an  ancient 
writer,  obscure  and  forgotten ;  or,  lastly,  they  maintain 
that  it  was  only  the  result  of  chance. 

I  do  not  know  whether  the  men  of  our  age  are  better 
than  their  predecessors  :  but  certainly  no  doubt  has  been 
raised  either  as  to  the  accuracy,  or  the  novelty,  or  the 
importance  of  the  discovei-ies  of  which  I  have  just  given 
an  account.     As  to  the  effect  of  chance,  the  blindest  envy 

plane  p,  pass  along  the  axis  of  rock  crystal  c,  of  the  thickness  x:  it 
emerges  polarized  in  a  new  plane  p',  inclined  to  p,  by  a  certain  angle. 
If  the  crystal  were  of  a  greater  thickness  i',  the  plane  would  be  turned 
still  further  into  the  position  p//,  at  t'  into  v"/^  and  so  on.  Thus  the 
successive  planes  of  polarization  formed  a  twisted  surface  like  a  cork- 
screw staircase.  In  some  crystals  this  twisting  takes  place  towards 
the  right,  in  others  towards  the  left.  The  change  of  plane  is  also  dif- 
ferent for  each  of  the  different  primary  coloured  rays.  Thus  exam- 
ined by  an  analyzer,  the  transmitted  ray  always  presents  a  succession 
of  colours. 

Sir  J.  Herschel  showed  that  the  right  or  left  handed  character  of 
the  polarization  agreed  with  the  like  inclination  of  the  small  facets  of 
the  complete  crystal  round  the  summit.  Biot  and  Seebeck  discovered 
the  same  property  to  exist  in  certain  liquids  such  as  oil  of  turpentine, 
and  even  in  some  vapours. 

The  phenomenon  is  explained  theoreticallj^  by  supposing  two  rays, 
each  circularly  polarized  in  opposite  directions,  traversing  the  axis 
together,  but  with  unequal  velocities.  In  this  case  it  is  shown  me- 
chanically that  the  resultant  of  such  vibrations  will  be  a  plane 
vibration  in  a  continually  changing  direction,  proportional  to  the 
retardation  which  one  of  the  rays  has  undergone,  behind  the  other, 
in  traversing  successive  thicknesses.  This  was  the  discovery  of 
Fresnel.  For  raj's  deviating  a  little  from  the  direction  of  the  axis, 
Mr.  Airy  showed  that  a  similar  theory  would  apply  with  eUipiicaRy 
polarized  light. 


THKORIES    OP   LIGHT.  231 

could  not  dare  to  appeal  to  it,  so  complicated,  so  minute, 
and  so  directly  designed  for  the  purpose  proposed  were 
the  experimental  means  employed  by  Fresnel  in  the  study 
of  circular  polarization.  Perhaps  it  may  be  proper  to 
observe  that  the  greater  part  of  them  were  suggested  by 
theoretical  ideas  ;  for  Avithout  that,  most  of  the  experi- 
ments of  our  colleague  offer  combinations,  of  which,  so  to 
speak,  it  would  seem  impossible  that  any  one  would  have 
thought.  If,  in  writing  the  history  of  the  sciences,  it  is 
just  to  put  in  their  full  light  the  discoveries  of  those  who 
have  cultivated  them  with  distinction,  it  is  important  also, 
— it  seems  to  me  right, — though  freely  stating  the  truth, 
yet  not  to  put  it  in  such  a  light  as  might  render  it  a  source 
of  discouragement  to  any  who  might  be  engaged  in  the 
same  pursuits. 

PRINCIPAL  CHARACTERISTICS    OF  THE    SYSTEM  OF  EMIS- 
SION AND  OF  THAT  OF  WAVES. GROUNDS  ON  WHICH 

FRESNEL  WAS    LED    TO    REJECT    UNRESERVEDLY  THE 
SYSTEM  OF  EMISSION. 

After  having  studied  with  so  much  care  the  properties 
of  luminous  rays,  it  was  natui-al  to  inquire  of  what  light 
consists  ?  This  scientific  question,  one  of  the  grandest, 
without  contradiction,  on  which  men  have  ever  occupied 
themselves,  has  given  occasion  for  the  most  animated  dis- 
cussion. Fresnel  took  an  active  part  in  it.  I  will  therefore 
endeavour  to  point  out  precisely  the  nature  of  the  ques- 
tion, and  give  a  concise  analysis  of  the  experiments  to 
which  it  has  given  rise. 

The  senses  of  hearing  and  smell  enable  us  to  discover 
the  existence  of  bodies  at  a  distance  by  totally  different 
means.  Every  odorous  substance  undergoes  a  species  of 
evaporation:  minute  particles  are  sent  off  from  it  inces- 


232  FRESNEL. 

santly,  they  mix  with  the  air,  which  becomes  a  vehicle 
for  them,  and  diffuses  them  in  every  direction.  A  grain 
of  musk,  whose  subtle  emanations  penetrate  through  all 
parts  of  a  vast  surrounding  circuit  loses  its  power  from 
day  to  day  ;  it  ends  by  being  entirely  dissipated  and 
totally  disappearing. 

It  is  not  the  same  with  a  sounding  body.  Eveiy  one 
knows  that  a  distant  bell,  whose  sound  strikes  faintly  on 
our  ear,  nevertheless  does  not  send  to  us  a  single  mole- 
cule of  metal ;  that  it  can  resound  without  interruption 
for  successive  centuries  without  losing  any  of  its  weight. 
When  the  clapper  strikes  it,  its  sides  vibrate,  they  undergo 
an  oscillatory  motion  which  communicates  itself  immedi- 
ately to  the  neighbouring  portions  of  the  air,  and  thence 
by  degrees  to  the  whole  atmosphere.  These  atmospheric 
vibrations  constitute  sound. 

Our  organs,  whatever  may  be  their  nature,  cannot  be 
put  in  relation  with  distant  bodies,  except  in  one  or  the 
other  of  these  two  ways  :  thus  either  the  sun  emits  inces- 
santly, as  odorous  bodies  do,  material  particles  from  all 
points  of  his  surface  with  a  velocity  of  77,000  leagues  in 
a  second,  and  these  are  minute  solar  fragments  which  by 
penetrating  into  the  eye  produce  vision ; — or  else  that 
luminary,  in  this  respect  like  a  bell,  excites  simply  an 
undulatory  movement  in  a  medium  extremely  elastic,  fill- 
ing all  space,  and  these  vibrations  proceed  to  agitate  our 
retinas  as  the  sonorous  undulations  affect  the  membrane 
of  the  tympanum. 

Of  these  two  explanations  of  tlie  phenomena  of  light, 
one  is  called  the  theory  of  emission,  the  other  is  known 
under  the  name  of  the  system  of  waves.*     We  find  long 

*  To  assist  the  general  conception  of  tlie  mode  of  propagation  of 
waves  by  transverse  vibrations,  perhaps  it  may  be  desirable  to  refer 


EMISSION    THEORY, 


233 


ago  traces  of  the  former  in  the  writings  of  Empedocles. 
Among  tlie  moderns  I  can  cite  among  its  adherents,  Kep- 
ler, Newton,  and  Laplace.  The  system  of  waves  does 
not  reckon  less  illustrious  partisans ;  Aristotle,  Descartes, 
Hooke,  Huyghens,  Euler,  adopted  it.  Such  names  on 
either  side  render  a  choice  difficult,  if  in  a  matter  of  sci- 

the  reader  to  a  very  simple  machine,  represented  in  the  annexed  figure 
contrived  by  the  translator,  which  exhibits  a  set  of  white  balls,  repre- 


senting the  molecules  of  ether:  these  are  attached  to  rods,  which  are 
moved  on  turning  the  handle  by  cranks  at  their  lower  end,  so  ai-ranged 
that  each  bull  is  in  succession  raised  or  lowered  nearly  in  a  straight 
line;  so  that  they  follow  each  other  in  the  form  of  a  wave.  When  the 
bar  supporting  the  rings  through  which  the  rods  pass,  is  lowered,  the 
balls  no  longer  move  up  and  down  in  straight  lines,  but  describe  each  a 
kind  of  oval  curve,  which  becomes  more  rounded  the  lower  the  bar  is 
placed.  In  the  former  case  the  machine  represents  a  wave  with  plain 
vibrations,  in  the  latter,  with  elliptic  or  circular  vibrations. 


234  fresneL. 

ence  the  most  illustrious  names  could  be  authorities  capa- 
ble of  determhiing  the  point. 

If,  liowever,  it  astonish  us  to  see  men  of  such  great 
genius  thus  divided,  I  would  say  that  in  their  times  the 
question  in  dispute  could  not  be  resolved  ;  that  the  neces- 
sary experiments  were  wanting  ;  and  that  then  the  two 
different  theories  of  light  were  not  logical  deductions 
from  facts,  but,  if  I  may  so  express  myself,  simple  mat- 
ters of  persuasion  ;  and  that,  in  a  word,  the  gift  of  infal- 
libility is  not  granted  even  to  the  most  skilful,  if  they 
transgress  the  bounds  of  observation,  and,  abandoning 
themselves  to  conjecture,  desert  the  strict  and  sure  path- 
by  which  science  advances  in  our  age  on  reasonable  prin- 
ciples, and  by  which  it  has  been  enabled  to  make  such 
incontestable  progress.  Before  we  review  the  great  in- 
roads which  have  been  recently  made  on  the  theory  of 
emission,  it  will  be  perhaps  convenient  to  cast  a  glance 
over  the  vigorous  attacks  of  which  it  was  the  object,  in 
the  writings  of  Euler,  of  Franklin,  and  others  ;  and  to 
show  that  the  partisans  of  Newton  might  then,  without 
looking  forward  too  much,  have  considered  the  solution 
as  adjourned  for  a  long  period.  Tlie  effects  which  a 
cannon  ball  can  produce  depend  so  directly  on  its  mass 
and  its  velocity  jointly,  that  we  can,  without  altering 
them,  change  at  pleasure  one  of  these  elements,  provided 
we  make  the  others  change  in  an  inverse  ratio.  Thus  a 
ball  of  two  kilogrammes  may  overthrow  a  wall ;  a  ball  of 
one  kilogramme  will  also  overthrow  it,  provided  we  im- 
press on  it  a  velocity  double  of  the  former.  If  the  weight 
of  the  ball  were  reduced  to  -^i^ih  or  xoiyth  of  its  original 
amount,  to  produce  the  same  effect  we  must  give  a  veloc- 
ity ten  times  or  one  hundred  times  as  great.  Now  we 
know  that  the  velocity  of  a  cannon  ball  is  the  640,000th 


EMISSION    THEORY.  235 

of  that  of  light ;  if  the  weight  of  a  luminous  molecule 
were  the  640,000th  part  of  that  of  the  cannon  ball,  it 
would  in  like  manner  overthrow  a  wall. 

These  deductions  are  certain :  but  let  us  look  at  the 
facts.  A  luminous  molecule  not  only  cannot  overthrow  a 
wall,  but  it  even  penetrates  into  an  organ  so  delicate  as 
the  eye  without  occasioning  the  least  pain,  without  even 
producing  any  sensible  dynamic  effect.  We  can  say 
more  :  in  experiments  undertaken  with  the  view  of  ren- 
dering sensible  the  impulsions  of  light,  physicists  have 
not  been  content  to  use  an  isolated  agent,  they  have 
brought  to  act  simultaneously  the  immense  quantity  of 
light  which  can  be  condensed  at  the  focus  of  a  large  lens  ; 
they  have  not  opposed  to  the  shock  of  the  rays  very  re- 
sisting objects,  but  bodies  so  delicately  suspended  that  a 
breath  could  derange  them  enormously ;  they  have  ope- 
rated for  example,  on  the  extremity  of  a  very  light  lever 
suspended  horizontally  by -a  spider's  thread.  The  sole 
obstacle  to  the  rotatory  movement  of  such  an  apparatus 
would  be  the  force  of  reaction,  which  the  thread  would 
acquire  in  twisting.  But  this  force  might  be  consid- 
ered as  nothing,  since  from  its  nature  it  always  increases 
rapidly  with  the  degree  of  torsion  ;  and,  in  this  instance, 
one  of  the  observers  whose  experiments  I  am  analyzing, 
found  no  perceptible  force  of  this  kind,  after  having  had 
the  patience  to  give  the  thread  14,000  turns,  by  turning 
the  lever  round  on  its  centre.  It  is  then  well  established 
that,  in  spite  of  their  excessive  velocity,  myriads  of  lumi- 
nous rays  acting  simultaneously  produce  no  jjerceptible 
force.  But  we  should  be  going  beyond  the  legitimate 
consequences  which  this  interesting  experiment  author- 
izes, if  we  concluded  that  a  ray  is  not  composed  of  mate- 
rial elements  endowed  with  a  rapid  motion  of  translation. 


236  FRESNEL. 

We  may,  indeed,  faii-ly  deduce  from  the  absence  of  all 
rotation  in  tlie  lever  suspended  by  tiie  spider's  thread, 
under  the  action  of  an  enormous  quantity  of  hght,  that 
the  elementary  particles  of  the  luminous  rays  have  not 
dimensions  comparable  to  the  millionth  part  of  the  finest 
molecules  possessing  any  weight.  But  as  there  is  nothing 
to  shovF  any  absurdity  in  supposing  them  a  million,  or  a 
myriad,  times  less  than  this,  this  kind  of  experiment  and 
argument  (the  first  idea  of  which  is  due  to  Franklin) 
cannot  furnish  any  decisive  conclusion. 

Among  the  objections  whicli  Euler  has  presented  in 
his  works  against  the  theory  of  emission,  I  will  point  out 
two,  on  which  he  has  particularly  insisted,  and  which 
seem  to  him  irresistible.  "•  If  tlie  sun,"  (said  this  great 
geometer,)  "continually  darts  out  particles  of  his  own 
substance  in  every  direction,  and  with  enormous  velocity, 
he  must  end  by  exhausting  himself:  and  during  the  many 
ages  which  elapsed  since  the  historical  period,  some  dimi- 
nution ought  already  to  have  become  sensible." 

But  is  it  not  evident  that  this  diminution  depends  on 
the  magnitude  of  the  particulars  ?  Now  there  is  nothing 
to  hinder  our  supposing  them  of  such  small  diameters 
that,  after  millions  of  years'  continual  emission,  the  mass 
of  the  sun  should  not  be  sensibly  altered.  And,  besides, 
there  is  no  accurate  observation  to  prove  that  this  lumi- 
nary does  not  waste,  or  that  its  diameter  is  really  as  great 
as  it  was  even  in  the  time  of  Hipparchus. 

No  one  is  ignorant  of  the  fact,  that  millions  of  rays  can 
penetrate  together  into  a  dark  room  through  a  pin-hole, 
and  there  form  distinct  images  of  external  objects.  In 
crossing  each  other  in  that  minute  space,  the  material 
elements  of  which  we  suppose  this  multitude  of  rays  to 
consist  ought,  nevertheless,  to  encounter  and  clash  against 


OBJECTIONS    TO    EMISSION.  237 

each  other  with  great  violence,  to  change  each  other's 
directions  in  a  thousand  ways,  and  to  mingle  together 
without  any  order.  This  difficulty  is  no  doubt  specious, 
but  it  does  not  appear  insurmountable. 

The  chance  that  two  molecules  setting  out  from  the 
same  hole  should  encounter  each  other,  depends  both  on 
the  absolute  diameter  of  the  molecules,  and  on  the  inter- 
vals which  separate  them.  We  might  then  by  suitably 
diminishing  the  diameters  reduce  the  chances  of  encoun- 
ter to  nothing.  But  we  have  here  also  in  the  intervals 
of  the  molecules  another  element,  which  alone  would  in 
a  great  degree  lead  to  the  same  conclusion.  In  fact 
every  sensation  of  light  lasts  for  a  certain  time  ;  the 
luminous  object  which  has  darted  its  rays  into  the  eye 
still  remains  visible  (as  experiment  has  proved)  at  least 
for  an  hundredth  of  a  second  after  the  object  has  dis- 
appeared. Now,  in  an  hundredth  of  a  second,  light  has 
gone  through  770  leagues.  Thus  the  luminous  mole- 
cules which  form  each  ray  may  be  at  770  leagues  inter- 
val from  one  another,  and  nevertheless  produce  a  con- 
tinuous sensation  of  light.  With  such  distances  what 
becomes  of  the  repeated  clashings  spoken  of  by  Euler, 
and  which  in  any  circumstances  ought  to  put  a  stop  to 
the  regular  propagation  of  the  rays  ?  It  is  almost  hu- 
miliating to"  see  a  geometer  of  so  rare  a  genius  believe 
himself  authorized  by  such  futile  objections  to  call  the 
system  of  emission  a  mistake  of  Newton, — a  gross  error, 
— the  belief  of  which,  he  says,  can  only  be  accounted  for 
by  recollecting  the  remark  of  Cicero,  "  There  is  nothing 
so  absurd  but  that  it  has  been  maintained  by  some  phi- 
losopher." * 

*  It  has  been  too  common  a  practice,  both  with  the  advocates  and 
the  opponents  of  the  wave  theory,  to  rest  its  defence  or  its  refutation 


238  FKESNEL. 

However,  the  system  of  emission  has  few  partisans  ; 
but  it  is  not  under  the  blows  dealt  by  Euler  that  it  has 

on  single  points ;  to  uphold  a  solitary  experimental  fact  as  decisive  one 
way  or  the  other.  A  single  favourable  fact  will  not  prove  the  theory ; 
and,  on  the  other  hand,  the  only  real  conclusion  in  cases  where  a 
single  fact  appears  to  stand  out  as  an  objection  is,  that  (granting  the 
fact  incapable  of  being  otherwise  interpreted)  the  theory  requires  re- 
modelling; and  that  some  undue  assumption  has  crept  into  it.  Such 
reconstruction  has  always  been  the  process  by  which  it  has  been  suc- 
cessively fouud  to  adapt  itself  to  nev/  phenomena,  even  when  at  first 
sight  they  appeared  most  opposed  to  it.  But  even  were  it  otherwise, 
the  theory  is  one  which  is  not  to  be  staked  on  single  facts;  it  rests  its 
claim  (in  the  first  instance)  in  being  that  which  connects  by  a  common 
principle,  and  tlms  explains  the  greatest  number  of  facts.  Many  of  the 
old  theories,  as  of  inflexion,  attractions,  &c.,  each  explained  a  certain 
small  number  of  facts;  but  the  real  argument  against  them  was,  that 
they  did  not  explain  each  other.  Every  new  partial  explanation  of 
the  wave  theory,  on  the  contrary,  not  only  explains  a  certain  class  of 
facts,  but  connects  these  with  some  other  class  similarly  explained. 
Newton  had  proposed  one  idea  (that  of  fits  of  easy  reflexion  and  trans- 
mission) to  account  for  the  altei'nations  in  the  colours  of  thin  plates; 
another  totally  unconnected  theorj"-  of  inflexion,  or  bending  in  and 
out  in  passing  the  edge  of  a  body,  to  explain  the  phenomena  of  dif- 
fraction: a  third  idea  of  polarity,  for  double  refraction;  besides  other 
occasional  references  to  waves,  or  even  a  combination  of  vibrations 
with  molecular  emission  in  some  cases;  but  all  unconnected  with,  and 
indejjendeni  of,  each  other,  and  each  confessedly  a  mere  arbitrary  as- 
sumption, not  pretending  to  stand  on  any  other  ground  than  that  it 
explained  in  a  certain  way  the  particular  phenomenon  in  relation  to 
which  it  was  adduced. 

On  the  undulatory  view,  on  the  contrary,  every  subordinate  law 
successively  established,  and  every  class  of  phenomena  explained, 
has  become  directly  connected  with  all  the  others.  Everj'  part  is  in 
intimate  relation  with  every  other  part,  and  the  progressive  improve- 
ment and  enlargement  of  the  theory  has  regularly  kept  pace  with  the 
advance  of  experimental  discovery;  every  new  modification,  as  it 
were,  has  grown  out  of  the  simple  principles  at  first  laid  down  by  a 
natural  sequence,  without  anj'  new  hypothesis,  or  forced  and  arbi- 
trary changes.  It  is  a  theory  of  which  an  eminent  philosopher,  by  no 
means  unduly  biased  in  its  favour,  and  at  a  time  when  it  had  by  no 
means  reached  its  present  point  of  perfection,  emphatically  said,  "  It 


VELOCITY    OF    LIGHT.  239 

fallen.  Insurmountable  objections  have  been  found  in 
various  phenomena  of  whose  very  existence  that  philos- 
opher was  necessarily  ignorant.  This  great  advance  in 
the  science  belongs  to  the  physicists  of  our  own  day,  and 
is  due  in  a  great  measure  to  tlie  labours  of  Fresnel. 
This  consideration  alone  obliges  me  to  point  them  out  in 
detail,  eren  if  the  interest  of  the  question  did  not  oblige 
me  to  do  so. 

If  light  is  a  wave,  the  rays  of  different  colours,  similar 
in  that  respect  to  the  sounds  employed  in  music,  are 
composed  of  vibrations  unequally  rapid  ;  and  the  red, 
green,  blue,  and  violet  rays,  are  transmitted  through  the 
ethereal  spaces,  as  are  all  the  notes  of  the  gamut  through 
the  air,  with  velocities  exactly  equal. 

If  light  be  an  emanation,  the  rays  of  different  colours 
are  formed  of  molecules  necessarily  different,  either  as  to 
their  nature,  or  their  mass,  and  which  besides  are  en- 
dowed with  different  velocities. 

An  attentive  inspection  of  the  borders  of  the  shadows 
produced  by  the  satellites  of  Jupiter  in  their  passage 
across  the  luminous  disk  of  the  planet,  and  better  still, 
the  observations  on  changeable  stars,  have  proved  that 
all  the  rays  of  light  move  equally  fast.  Thus  a  charac- 
teristic feature  of  the  system  of  waves  is  found  verified. 

In   each  of  the   two   systems   of  light  *  the   original 

is  a  series  of  felicities;  and  if  not  true,  eminently  deserves  to  be  true." 
And  the  increasing  proof  which  it  continues  to  receive  by  its  readi- 
ness in  meeting  nearly  everj'  new  experimental  case  as  it  arises,  aug- 
ments in  the  same  proportion  our  conviction  that  it  will  sooner  or 
later  be  equally  successful  in  the  solution  of  those  few  phenomena, 
which  still  appear  to  stand  out  as  exceptional  instances  to  its  appli- 
cation.—  Translator. 

*  When  the  author  affirms  that  in  each  of  the  two  theories,  (dans 
I'un  et  dans  I'autrc  des  deux  systemes,)  the  original  velocity  of  a  ray 
determines  its  refraction,  there  seems  to  be  a  certain  degree  of  con- 


240  FRESNEL. 

velocity  of  a  ray  determines  the  refraction  which  it  must 
undergo  when  it  falls  obliquely  on  the  surface  of  a  trans- 
fusion, which  it  is  difficult  to  explain.  The  assertion  is  clear,  and  the 
whole  subsequent  argument  agrees  with  that  assertion,  in  rtgard  to 
the  emission  theory.  Here,  undoubtedly,  the  original  velocity  with 
which  a  ray  enters  a  new  medium,  when  it  is  acted  upon  by  the 
attractions  of  a  number  of  surrounding  particles,  will  essentially  deter- 
mine the  velocity  with  which  it  will  continue  to  move  under  the  in- 
fluence of  these  attractions,  and  the  path  it  will  take.  But  on  the  icave 
theory  there  appears  nothing  obviously  and  antecedently  to  show  what 
will  be  the  case. 

The  author  proceeds,  as  if  continuinf/  the  last  topic,  to  quite  another 
point,  viz:  the  experimental  fact  that  light  from  the  most  different 
sources,  both  terrestrial  and  celestial,  moves  with  precisely  the  same 
velocity  throuyh  air  or  vacuum.  He  argues  that  this  is  a  "  mathe- 
matical consequence"  of  the  wave  theory;  because,  in  the  parallel 
case  of  sound,  tones  produced  by  the  most  different  instruments  are 
propagated  through  the  air  with  the  same  rapidity.  It  is  certainly  a 
close  analogy,  but  hardly  a  "  mathematical  consequence."  The  re- 
mai-k  which  follows  as  to  the  consequence  of  molecular  theory,  in 
rendering  light  from  different  sources  unequally  rapid  in  its  flight 
from  their  differences  of  attractive  power,  presents,  no  doubt,  a  formi- 
dable difficulty  to  that  theory,  as  being  in  contradiction  to  the  experi- 
mental result  just  mentioned. 

But  when  in  reference  to  his  own  beautiful  experiment  on  observing 
the  refractions  of  light  when  its  velocity  is  respectively  increased  and 
diminished  by  the  whole  velocity  of  the  earth,  he  adds,  "  such  rays 
ought  to  be  unequally  refracted,"  I  can  only  understand  the  mean- 
ing by  referring  to  the  mention  made  of  the  emission  theory  in  the 
next  line,  and  supposing  that  theory  alone  to  be  intended.  On  thai 
theory,  it  is  true,  such  rays  ought  to  be  unequally  refracted. 

Observation,  however,  gives  a  perfect  equality  of  refraction  in  the 
two  cases,  and  thus  far  completely  contradicts  the  idea  of  molecular 
attractions.  And  when  he  adds,  that  the  only  way  in  which  this 
contradiction  could  be  reconciled  with  emission,  would  be  by  invent- 
ing the  subsidiary  gratuitous  hypothesis  that  the  stars  emit  an  infinite 
number  of  rays,  endowed  with  all  possible  velocities,  and  that  only 
those  of  a  certain  velocity  can  affect  our  organs  with  the  sense  of 
vision,  this  would  obviously  only  be  to  add  "  cycle  on  epicycle,"  "  to 
save  appearances,"  and  would  afford  no  real  explanation.  On  the 
other  hand,  with  respect  to  the  undulatory  theory,  it  does  not  appear 


VELOCITY    OF    LIGHT.  241 

parent  bodj.  If  this  velocity  increase,  the  refraction 
will  be  less,  and,  reciprocally,  a  diminution  of  velocity 

that  it  would,  on  any  obvious  a  pricn-i  grounds,  enable  us  to  predict 
the  result  of  such  an  experiment  one  way  or  the  other.  There  is 
indeed  involved  the  difficult  and  complex  consideration  of  the  propa- 
gation of  vibrations  through  eether,  while  the  earth  and  transparent 
media  upon  it  are  moving  through  that  cether;  a  problem  which  ex- 
ercised the  ingenuity  of  Fresnel,  and  which,  after  a  long  investigation, 
he  decided  by  concluding  that  the  effects  would  be  exactly  the  same 
as  if  the  earth  were  at  rest.  This,  however,  may  be  still  regarded  as 
one  of  those  points  connected  with  what  is  the  most  difficult  part  of 
the  wave  theory,  viz :  the  primary  conception  of  a3ther  and  its  prop- 
erties. 

But  apart  from  this  consideration,  and  looking  only  to  the  abstract 
problem  of  light  (suppose  emitted  on  the  surface  of  the  earth)  falling 
on  a  refracting  body  with  cUfftrent  velocities,  there  is  nothing  appar- 
ently in  theory  to  determine  whether  the  refraction  will  be  affected, 
or  in  what  way,  by  this  difference. 

On  the  undulatory  principle,  it  is  true,  velocity  is  intimately  con- 
nected with  refraction ;  retardation  and  refraction  being  c'oextensive 
and  almost  equivalent  terms ;  but  it  must  be  borne  in  mind  that  it  is 
not  absolute  but  relative  velocity  which  is  thus  connected  with  refrac- 
tion. It  is  the  relative  retardation  in  the  denser  medium,  whatever 
the  absolute  velocity  may  be,  which  causes  refraction.  If  in  theory  it 
were  shown  that  the  ratio  would  be  constant  for  all  velocities,  it 
would  give  a  constant  refraction  for  the  medium.  But  this  is  the 
verj'  point  in  question ;  and  there  appears  nothing  antecedently  to 
show,  on  any  distinct  theory  of  the  nature  of  asther  or  of  waves,  that 
the  relative  velocities  must  necessarily  be  in  a  constant  ratio.  There 
is,  however,  nothing  in  any  conception  of  waves  at  variance  with  the 
idea;  and  it  must  be  admitted  as  in  itself  a  rational  and  probable  sup- 
position, fairlj'  admissible  in  the  first  instance  to  ground  any  reason- 
ing upon.  When  therefore  the  fact  was  established  by  Arago's 
experiment,  while  it  completely  subverted  what  was  a  necessary 
consequence  of  the  emission  theory,  it  offered  no  contradiction  to  the 
undulatory;  but  the  proposition  it  established  being  one  already />ro6- 
Me,  and  consistent  with  that  theory,  was  now  to  be  recognized  as  an 
essential  part  of- it.  Yet  the  result  of  Arago's  experiment  has  been 
represented  by  some  able  wTiters  as  of  a  very  startling  and  unex- 
pected nature,  and,  at  first  sight,  equally  perplexing  on  either 
hypothesis. 

SEC.   SEE.  11 


242  FRESNEL. 

will  manifest  itself  by  an  increasing  deviation.  Refrac- 
tion thus  becomes  a  sure  means  of  comparing  the  veloci- 
ties of  all  sorts  of  rays.  In  following  out  this  research 
with  experimental  means  so  precise  that  they  would 
mark  ditferences  of  one  fifty-thousandth  part  of  the  wliole 
amount  in  (juestion,  we  have  been  able  to  ascertain  that 
tlie  light  of  all  the  heavenly  bodies, — of  our  fires,  of 
tapers,  and  lamps,  (with  double  currents  of  air,)  and 
even  more,  the  feeble  rays  emitted  by  glow-worms,  all 
go  through  77,U00  leagues  in  a  second,  as  well  as  the 
burning  light  of  the  sun. 

It  is  easy  to  conceive  in  what  way  this  result  is  a 
mathematical  consequence  of  the  system  of  ivaves,  if  we 
only  remark  that  all  the  notes  of  the  musical  scale  are 
propagated  with  equal  rapidity  thi-ough  the  air,  whether 
they  originate  from  the  voice  of  a  singer,  from  the  metal- 
lic string  of  a  piano,  the  catgut  of  a  violin,  the  glass  sur- 
face of  an  harmonica,  or  the  metallic  sides  of  the  great 
pipe  of  an  organ.  Now,  there  is  no  reason  why  the 
luminous  notes  (if  I  may  be  pardoned  the  expression) 
sliould  proceed  differently  in  lether.  On  the  hypothesis 
of  emission  the  explanation  is  not  so  simple.  If  light  is 
composed  of  material  elements,  it  would  find  itself  sub- 

The  luidultitory  view  of  refraction  depends  entirel}^  on  the  assump- 
tion that  the  velocity  must  be  diminished  in  the  denser  medium;  but 
as  the  refraction  is  proved  to  be  constant  for  all  velocities,  this  dimin- 
ished velocity  must  be  always  in  a  constant  ratio  to  the  original  veloc- 
ity. This  is  the  condition  to  which  our  conception  of  aether  must 
conform.  As  to  the  fact  of  a  retardation,  that  has  been  directly 
proved  by  another  beautiful  experiment  devised  by  Arago,  but  car- 
ried out  by  the  experimental  skill  of  Foucault,  on  the  principle  of 
Wheatstone's  levolving  mirror,  which,  if  it  received  one  of  two  rays 
at  the  smallest  interval  of  time  fl/?e?' another,  would  reflect  it  in  a  dif- 
ferent direction.  Thus  the  existence  of  any  retardation  in  one  of  tiie 
rays  would  be  manifested. 


EXPERIMENT    ON    VELOCITY.  243 

jeet  to  universal  attraction  ;  it  would  with  difficulty  be 
darted  out  from  an  incandescent  body,  because  the  attrac- 
tion of  that  body  will  tend  to  carry  it  back  again  ;  hence 
a  gradual  diminution  of  its  original  velocity  must  un- 
doubtedly take  place  ;  it  is  only  necessaiy  to  inquire 
whether  observation  can  enable  us  to  discover  it.  It 
would  be  a  simple  question  of  calculation  how,  in  mak- 
ing some  suppositions  with  respect,  to  the  physical  con- 
stitution of  certain  fixed  stars  in  respect  to  their  size  and 
density,  which  do  not  appear  extravagant,  we  find  that 
they  may,  by  their  attractive  force,  annihilate  altogether 
the  velocity  of  emission  of  luminous  molecules ;  that 
after  having  j^roceeded  to  a  given  distance,  these  mole- 
cules, which  had  so  far  separated  themselves  from  the 
body,  must  return  thither  by  a  retrograde  movement. 
Thus,  certain  stars  might  be  as  luminous  as  the  sun,  to 
the  distance  of  40,000,000  leagues,  for  example,  and 
beyond  that  be  altogether  dark  ;  that  distance  being  the 
exact  limit  beyond  which  none  of  their  rays  could  pass. 
If  we  change  considerably  the  volumes  and  densities 
which  give  these  results  ;  if  we  assume  for  stars  of  the 
first  magnitude  such  dimensions  as  no  astronomer  would 
refuse  to  consider  as  probable,  they  will  no  longer  pre- 
sent such  strange  phenomena,  they  will  no  longer  be 
dazzling  at  this  distance,  and  completely  dark  at  a  little 
farther  distance  ;  but  the  velocity  of  their  light  will 
change  with  the  distance ;  and  if  two  such  stars  are  at 
very  difierent  distances  from  the  earth,  their  rays  will 
arrive  at  our  eyes  with  dissimilar  velocities.  Is  it  not 
then  a  formidable  objection  against  the  theory  of  emis- 
sion, that  there  should  be  this  perfect  equality  of  velocity 
in  all  cases,  which  all  observations  testify  ? 

There  exist  very  simple  means  for  altering  to  a  nota- 


244  FRESNEL. 

ble  extent,  if  not  the  absolute,  yet  the  relative  velocity 
of  a  ray  ;  it  is  to  make  observations  on  it  when,  in  the 
annual  course  of  the  earth,  its  motion  is  directed  towards 
the  star  from  which  the  ray  proceeds,  and  again  when  it 
is  diametrically  in  the  opposite  direction.  In  the  former 
case,  it  is  as  if  the  velocity  of  the  ray  was  increased  by 
the  whole  of  that  of  our  globe  ;  in  the  second,  the  nu- 
merical difference  has  the  same  amount,  but  the  velocity 
is  diminished.  Now  no  one  is  ignorant  that  the  velocity 
of  the  earth's  revolution  is  quite  comparable  with  that  of 
light  ;  being  in  fact  about  a  ten-thousandth  part  of  it. 
And  again  ;  to  observe  a  star,  towards  which  the  earth 
is  moving,  and  then  one  from  which  it  is  receding,  is  to 
operate  upon  rays  whose  velocities  differ  from  each  other 
by  one  five-thousandth  part.  Such  rays  ought  to  be 
unequally  refracted  ;  the  theory  of  emission  furnishes 
the  means  of  expressing  in  numbers  the  amount  of 
the  inequality  ;  and  we  may  easily  see  that  it  will  far 
exceed  the  small  errors  of  observation.  Now  precise 
measures  have  completely  negatived  such  calculation  ; 
the  rays  proceeding  from  all  stars,  in  whatever  region 
they  are  situated,  undergo  precisely  the  same  refraction. 

The  disagreement  between  this  theory  and  experience, 
could  not  be  more  manifest,  and  from  that  moment  the 
system  of  emission  seemed  to  be  overturned  from  its  very 
foundations.  Nevertheless,  this  definitive  sentence  has 
been  suspended  by  the  aid  of  a  supposition  which  I  can 
explain  in  two  words ; — it  consists  in  admitting  that 
incandescent  bodies  emit  rays  with  all  sorts  of  velocities, 
but  that  a  special  and  determined  velocity  is  necessary 
to  make  them  rays  of  light.  If  a  ten-thousandth  part  of 
increase  or  diminution  in  their  velocity  takes  away  from 
rays  their  luminous  properties,  the  observed  equality  of 


ACTION    OP    LIGHT    ON    CERTAIN    BODIES.  245 

deviation  is  the  necessary  consequence  of  this  supposi- 
tion, since  in  the  muhitutle  of  rays  which  strike  on  the 
eye,  wliether  it  is  apparently  towards  or  receding  from 
the  stars,  it  will  perceive,  in  either  case,  those  only  whose 
molecules  have  the  same  relative  velocity  ;  but  this 
hypothesis,  it  cannot  be  denied,  deprives  the  system  of 
emission  of  the  simplicity  which  constitutes  its  main 
recommendation.  The  clashing  of  molecules  on  which 
Euler  so  much  insisted,  would  then  become  the  inevita- 
ble consequence  of  their  inequality  of  velocity,  and  w^ould 
entail  on  the  propagation  of  the  rays  disturbances  to 
which  observation  does  not  show  them  to  be  subject. 

Light  exercises  a  striking  action  on  certain  bodies  ;  it 
rapidly  changes  their  colour.  Nitrate  of  silver,  as  is  well 
known,  possesses  for  example  this  power  in  a  high 
degree.  It  suffices  to  expose  it  for  a  few  seconds  to  the 
diffuse  light  of  a  cloudy  sky  for  it  to  lose  its  original 
whiteness,  and  to  become  of  a  bluish  black.  In  the  rays 
of  the  sun  it  changes  almost  instantaneously.  Chemists 
have  believed  that  they  could  see  in  this  discoloration  a 
phenomenon  analogous  to  that  they  produce  every  day. 
According  to  them  the  light  would  be  a  true  "reagent," 
which  in  being  added  to  the  constituent  principles  of  the 
compound  on  which  it  acts,  sometimes  modifies  its  origi- 
nal properties ;  sometimes  also  the  luminous  matter  only 
determines  by  its  action  the  disengagement  of  one  or 
more  elements  of  the  body  on  which  it  strikes. 

These  explanations,  although  based  on  specious  analo- 
gies, do  not  seem  to  be  admissible,  since  it  has  been 
shown  that,  in  interfering,  the  luminous  rays  also  lose 
the  chemical  properties  with  which  they  are  endowed. 
How  can  we  conceive,  in  fact,  that  the  matter  of  two 
rays   can   combine   with   a  given  substance  if  each  ray 


246  FRESNEL. 

strike  it  singly,  while  on  the  contrary  no  such  combina- 
tion can  take  place  when  these  same  rays  strike  it 
together,  after  having  pursued  (for  this  condition  is 
necessary)  routes  ditfering  from  one  another  by  quan- 
tities comprised  within  a  certain  regular  series  of  num- 
bers ? 

In  geometry,  in  order  to  demonstrate  the  inaccuracy 
of  a  proposition,  we  follow  it  out  to  all  its  consequences 
until  there  results  something  which  is  completely  absurd. 
Ought  we  not  to  class  in  this  category  a  chemical  action 
which  is  generated,  or  which  disappears,  according  to 
the  length  of  route  which  the  reagent  has  gone  through  ? 
Natural  phenomena  ordinarily  present  themselves  un- 
der very  complicated  forms,  and  the  true  merit  of  the 
experimenter  consists  in  disengaging  them  from  a  multi- 
tude of  accessory  circumstances  which  hinder  us  from  at 
once  seizing  their  laws. 

If,  for  example,  we  had  not  observed  the  shadows  of 
bodies  except  in  the  open  air,  if  we  had  never  illuminated 
these  bodies  by  light  proceeding  from  extremely  small 
luminous  points,  no  one  would  have  guessed  how  many 
curious  subjects  of  research  are  offered  by  a  phenomenon 
so  common.  But  place  in  the  middle  of  a  dark  room, 
and  in  a  beam  of  homogeneous  light,  diverging  either 
from  a  minute  hole,  or  from  the  focus  of  a  glass  lens,  any 
opaque  body  whatever,  and  its  shadow  will  show  itself 
marked  by  a  series  of  contiguous  stripes,  alternately 
bright,  and  completely  dark.  Substitute  white  light  for 
the  homogeneous  beam,  and  similar  stripes  vividly  col- 
oured will  appear  to  occupy  the  place  of  the  former. 

Grimaldi  first  perceived  these  singular  affections  of 
light,  to  which  he  gave  the  name  of  diffraction.  Newton 
afterwards  made  them  the  subject  of  a  special  investiga- 


DIKFUACTION.  247 

tion ;  he  thought  he  saw  here  the  manifest  proofs  of  an 
intense  attractive  and  repulsive  action,  which  bodies 
exercise  on  rays  passing  close  to  them.  This  action, 
supposing  it  real,  could  only  be  explained  by  admitting 
the  materiahty  of  light.  The  phenomena  of  diffraction, 
then,  deserves  in  an  eminent  degree  to  fix  the  attention 
of  physicists.  Many  in  fact  studied  it,  but  by  very 
inexact  methods ;  Fresnel  finally  gave  to  this  class  of 
observations  a  perfection  unhoped  for,  in  showing  that 
in  order  to  see  these  diffracted  bands,  it  is  not  necessary 
to  receive  them  on  a  screen,  as  Newton  and  all  the  other 
experimenters  had  done  hitherto  ; — that  they  are  found 
distinctly  in  space,  where  we  can  follow  them  with  all 
the  resources  which  result  from  the  employment  of  the 
astronomical  micrometer,  with  a  high  magnifying  power. 

According  to  the  precise  observations  of  Fresnel,  by 
the  aid  of  these  new  modes  of  observation,  if  we  still 
wish  to  attribute  the  effects  of  diflTraction  to  attractive  or 
repulsive  forces  acting  on  material  elements,  we  must 
admit  that  these  actions  are  totally  independent  of  the 
nature  or  density  of  the  bodies  employed,  for  a  spider's 
thread  and  a  wire  of  platinum  produce  bands  exactly 
the  same ;  the  masses  have  no  more  influence,  since  the 
back  and  the  edge  of  a  razor  produce  the  same  effect. 
We  find  ourselves  inevitably  brought  to  this  conclusion, 
that  a  body  acts  on  the  rays  passing  near  its  surface  with 
so  much  the  less  energy  as  the  rays  come  from  a  greater 
distance,  since,  if  on  placing  the  luminous  point  at  the 
distance  of  a  centimetre,  the  angular  deviation  is  12,  it 
will  not  amount  quite  to  4  in  similar  circumstances  with 
light  coming  from  ten  times  the  distance. 

These  various  results,  especially  the  last,  are  impos- 
sible to  reconcile  with   any  idea  of  an  attraction.     The 


248  FRESNEL. 

experiments  of  Fresnel  destroy  entirely  all  the  arguments 
which  had  been  relied  on  in  the  phenomena  of  diffrac- 
tion to  establish  the  materiality  of  light. 

The  important  branch  of  optics  which  treats  of  the 
intensity  of  reflected  light,  transmitted  and  absorbed  by 
bodies,  which  is  designated  by  the  name  of  photometry, 
is  but  in  its  infancy  ;  it  at  present  consists  of  nothing 
more  than  isolated  results,  whose  exactness  may  be  open 
to  much  question.  General  mathematical  laws  are 
wholly  wanting.  Some  attempts  made  a  few  years  ago 
have,  however,  led  to  a  very  simple  rule  which,  for 
every  kind  of  transparent  media,  connects  the  angles  of 
the  first  and  second  surface  at  which  the  reflexions  are 
equal.* 

*  The  measures  of  intensity  of  light  here  alluded  to  are  those  of 
M.  Poisson;  which,  however,  were  in  a  great  degree  anticipated  by 
Dr.  Young  [Chromatics,  Encycl.  Brit.'],  though  Poisson  calls  his 
reasoning  indirect,  an  opinion  in  which  Sir  J.  Herschel  says  he  can- 
not concur.  Poisson  takes  the  case  of  perpendicular  incidence, 
and  adopts  the  hypothesis  of  the  vibrations  being  coincident  with  the 
direction  of  the  ray  ;  he  thus  obtains  expressions  for  the  relative  inten- 
sities of  the  incident,  reflected,  and  transmitted  rays;  and  thence, 
again,  of  the  ray  reflected  at  the  second  surface.  These  result  in 
terms  of  the  index  of  refraction.  Arago  applied  this  principle  {as  far 
as  any  photometrical  measurements  can  be  relied  on)  for  the  intensity 
of  light  reflected  from  Mercury  to  determine  its  refractive  index.  The 
formula  of  Young  is  derived  from  the  analogy  of  the  motion  commu- 
nicated from  a  portion  of  eether  in  one  medium,  to  that  in  a  difi'erent 
state  of  density  in  another,  with  that  of  the  impact  of  unequal  elastic 
bodies,  and  mthoui  any  asmmptioniy=>  to  the  direction  ot  the  vibrations; 
the  same  principle  on  which  the  formulas  of  Fresnel  are  deduced  in 
Mr.  Airy's  Tract,  (Art.  128.)  See  Sir  J.  Herschel  on  Light,  Art. 
592;  and  Lloyd's  Lectures  on  the  Wave  Theory,  p.  31. 

Mathematically,  Young's  formula  is  deduced  in  this  way.  Km  and 
m'  be  the  masses  of  two  elastic  bodies,  m  impinging  on  m'  at  rest,  by 
the  principles  of  mechanics  (the  velocity  of  m  being  unity)  it  is  well 
known  that  after  impact  m  retains  a  velocity 


REFLEXION    OF    POLARIZED    LIGHT.  249 

In  the  system  of  emission  these  two  angles  have  no 
necessary  dependence ;  the  contrary  is  the  case  if  the 
luminous  rays  are  sets  of  waves,  and  the  relation  which, 
in  setting  out  from  this  hypothesis,  one  of  our  most  dis- 
tinguished colleagues  has  deduced  from  his  scientific 
analysis  is  precisely  that  which  experience  has  fur- 
nished. Such  an  accordance  between  calculation  and 
observation  ought  at  the  present  day  to  take  its  place 
among  the  most  forcible  arguments  which  we  can  pro- 
duce on  which  to  support  the  system  of  vibrations. 

/  m  —  mi  \ 
VI  =  [        ,      ,    )  (1.) 

\.  m  +  ml   I 

and  ml  receives  a  velocity 

„=(_1^>)  (2.) 

\  m  -|-  m,i   ) 

It  is  also  assumed  that  this  analogy  may  be  applied  to  a  mass  of 
aether  (m)  in  vibration  outside  the  reflecting  surface,  and  communi- 
cating its  vibrations  partly  to  another  mass  (ml)  at  rest  within  the 
medium;  these  masses  are  dependent  on  and  partly  retaining  it  in 
reflexion.  Dependent  on  the  densities,  in  two  contiguous  media,  and 
the  inclination  of  the  ray. 

At  a  perperulicular  incidence  the  two  masses  are  simply  proportional 

m         1 
to  the  densities  or  of  the  refractive  powers;    oi"  ^  =  "17  '    hence   in 

this  case  the  velocity  of  the  incident  ray  being  taken  as  unity,  that  of 

the  reflected  ray  will  be  (  —  j  and  according  to  the  principle  of 

vis  viva  the  intensity  will  be  proportional  to  the  square  o^  this  quantity. 
This  is,  however,  only  a  particular  case  of  the  general  formulas  dis- 
covered by  Fresnel,  and  applying  universally  to  intensities  of  reflected 
light  at  all  incidences.  The  demonstration  of  these  formulas  in- 
volves some  difficulties  which  Fresnel  did  not  clear  up,  but  which  he, 
with  marvellous  sagacity,  got  over  by  suppositions  somewhat  of  an 
empirical  and  hypothetical  kind.i  To  express  the  masses  of  the  cor- 
responding vibrating  portions  of  cether  in  the  two  adjacent  media,  we 
take  lengths  I  and  li  of  the  incident  and  refracted  rays  inversely  pro  - 

1  See  Mr.  Airy's  Tract  of  the  Undulatory  Theory.  Art.  128, 
ct  seq. 

11* 


250  FRESNEL. 


The  interferences  of  rays  have  occupied  so  great  a 
space  in    this    biography   that    I    cannot    dispense  with 

portional  to  their  refractions  or  retardations,  or  inversely  as  the  den- 
sities, that  is,  as  sin  r;   sin  i ;    and  drawing  parallels   to  them,  the 


breadths  of  the  parallelograms  on  the  same  base  are  easily  seen  to  be 
in  the  ratio  of  cos  i;  cos  r,  and  thus  the  ratio  of  the  simultaneously 
vibrating  masses  is, 

m  sin  r  cos  i 

mi  sin  i  cos  7- 

Hence  Fresnel  deduced  for  vibrations  parallel  to  the  plane  of  inci- 
dence the  ratio  of  the  amplitudes,  that  of  the  incident  ray  being 
unity, 

sin  2  i  —  sin  2  ?•         tan  (i  —  r\  ,„  . 

reflected  h'  =     .    „  .   ,     .  -„—  =    ,     )■,     !  (3-) 

sui  2  I  -1-  sin  2  »•  tan  {i  -f-  r) 

4  sin  r  cos  i  f^        tan  (i — r)  v    cos  J. 

refracted  A;/ = -^—^ r— r — =(1— -^ — -r- — ;  )  — —  -     (4-) 

sm  2  I -h  sm  2  r  ^  tan  (i-|- »•)  y  cos  r. 

For  vibrations  perpendicular  to  the  plane  of  incidence  he  found, 

^^^_^n(i^  (5.) 

sm(t+  r) 

,         2  sin  r  cos  i  ,„  . 

sm  (t+r) 
As  to  the  mode  of  deducing  these  formulas,  considerable  discussion 
has  arisen,  and  the  question  cannot  be  regarded  as  yet  settled. 

On  merely  geometrical  grounds,  the  directions  of  the  incident  re- 
flected and  refracted  rays  are  seen  to  form  a  triangle,  whose  angles 
are  (i  +  r),  (» —  r),  and  tt  —  2  i),  and  their  sines  being  as  the  opposite 
sides  h  h'  hi  we  have,  considering  h  for  the  incident  ray  as  unity. 


REFLEXION    OF    POLARIZED    LIGHT. 


251 


pointing  out  how  they  are  connected  with  the  two  theo- 
ries of  light ;  liow  in  the  theory  of  emission  I  do  not 

values   very  much   resembling   the  last    yet  difl'eriug  from    them; 
viz: — 

sin  (i  —  »•)      _  ,  sin  2  i 


hi: 


Cr.) 


hi 


(8.) 


sin.  (i+r)     '"'  "'       sin  (i  +  r) 

If  we  draw  lines  perpendicular  to  the  directions  of  these  rays,  they 


■will  also  form  a  similar  triangle,  among  whose  sides  the  same  rela- 
tions will  subsist.  Hence,  Pi-ofessor  Maccullagh  inferred  that  these 
would  represent  the  directions  of  the  vibrations  in  the  plane  of  inci- 
dence ;  and  as  the  lengths  or  amplitudes  of  these  vibrations  are  un- 
known, but  are  dependent  upon,  as  they  are  the  measures  of, — the 
vibratory  forces  acting, — so  if  one  of  the  sides  of  the  triangle  be 
assumed  to  represent  the  magnitude  of  the  incident  vibration,  the 
others  will  represent  those  of  the  reflected  and  refracted  rays,  thev 
being  the  mechanical  components  of  which  the  former  is  the  resul- 
tant. 

On  this  construction,  and  by  assuming  the  hypothesis  of  equal 
density  within  and  without  the  medium,  he  deduced  the  above  form- 
ulas (7.)  (8.)  for  vibrations  parallel  to  the  plane  of  incidence,  and 
others  resemhling  (3.)  and   (4.)   for  vibrations  perpendicular  to  that 


252  PRESNEL. 

hesitate  to  say,  if  we  admit  no  dependence  between  the 
motions  of  the  different  luminous  molecules  (and  I  know 

pliine,  thus  differing  essentially  from  the  former.  See  Professor  Mac- 
cullagh's  paper  "  On  the  Laws  of  Crystalline  Refraction,"  Transac- 
tions of  the  Irish  Academy,  vol.  xviii. ;  and  Dr.  Lloyd's  Lectures  on 
the  Wave  Theory,  part  ii.  p.  30.  The  whole  subject  has  been  fully 
discussed  by  the  Translator  in  three  papers  in  the  Philosophical  Mag- 
azine for  July,  August,  and  October,  1856. 

The  demonstration  in  either  case  is  grounded  on  the  assumption  of 
the  law  of  vis  viva ;  viz : 

m  {Ifi  —  7ti2)  =  im  hi^. 

And  Fresnel's  fonnulas  would  be  directly  deduced  if  we  had  also 
the  relations 

h  ■\-  h'  =:hi  for  vibrations  perpendicular  to  the  plane  of  incidence, 

and  h  —  h'  =.hi  ....  parallel  to  the  plane  of  incidence. 

cos  I 

The  difficulty  is,  that  these  formulas  are  not  both  deducible  from 
the  principle  of  equivalent  vibrations  as  laid  down  by  Professor 
Maccullagh.  Another  mode  of  deduction,  on  a  different  assumption, 
is  pointed  out  in  the  Philosophical  Magazine  for  Oct.  1855,  by  means 
of  the  geometrical  construction  above  given. 

The  theory  of  Fresnel,  it  will  be  easily  seen,  is  equivalent  to  the 
assertion  that  "  the  plane  of  vibration  is  perpendicular  to  the  plane  of 
polarization,"  whereas  in  that  of  Maccullagh  they  are  coincident. 

Several  classes  of  experiments  have  been  now  shown  to  necessitate 
the  adoption  of  the  former  view:  for  an  account  of  which  the  reader 
is  referred  to  the  Philosophical  Magazine  for  Aug.  1856,  before  cited. 

To  proceed  to  the  ajipUcations  of  these  formulas :  we  may  consider 
common  light  as  consisting  of  two  portions  of  equal  intensity,  polar- 
ized at  right  angles  to  each  other.  If  the  intensity  of  the  incident 
light  be  1,  that  of  each  of  these  components  will  be  i.  At  reflexion 
each  component  gives  a  reflected  and  a  refracted  ray  polarized  re- 
spectively at  right  angles.  In  the  reflected  ray  the  intensity  of  the 
portion  polarized  in  the  plane  of  incidence  (i)  will  be  =  i  /t'2.  That 
in  the  plane  perpendicular  to  (k)  will  be  =  i  ki"^,  and  it  is  easily  seen, 
from  the  nature  of  the  fractions,  that  of  these  quantities  the  first  will 
always  be  the  greater;  and  thus  in  their  sum  or  the  total  intensity 
there  will  be  an  excess  of  light  polarized  in  the  plane  of  incidence,  or 
the  light  is  at  all  incidences  partially  polarized  in  the  plane  of  inci- 
dence. The  difference  of  the  two  expressions  gives  the  quantity  of 
light  so  polai'ized. 


REFLEXION    OF    POLARIZED    LIGHT.  253 

not  what  dependence  we  can  establish  between  isolated 
projectiles),  the  fact,  and  above  all  the  laws,  of  inter- 
In  the  refracted  ray  the  intensities  of  the  residuary  portions  respec- 
tively will  be 

1  {l  —  h'-2)  ini 
i  il  +  k'-2)  in  K. 
Here  the  second  is  always  the  greater:  and  the  refracted  ray  con- 
tains an  excess  of  light  polarized  perpendicularly  to  the  plane  of  inci- 
dence. The  difference  or  quantity  of  light  polarized  is  the  same  as  in 
the  reflected  ray.  Hence  the  light  will  be  completely  polarized  at 
any  incidence  for  which  either  of  the  expressions  (3.)  or  (5.)  vanishes. 
No  value  of  i  will  make  (5.)  vanish,  since  we  can  never  have  i  =  r. 
But  the  expression  (3.)  becomes  =  0  when  i-l-9'=90°.  In  this  case 
the  light  is  comjAetely  polarized  in  the  plane  of  incidence.  But  in  this 
case  we  have  also 

sin  i        .       .      ,1 
cos  I  =  sin  r  = or  tan  i  =  H; 

which  is  Brewster's  law  ;  also  if  i  +  r  "^90"  we  have  —  tan  (i  +  r). 

Also  at  this  incidence  h.  the  incident  light  is  reflected,  wholly  polar- 
ized in  I;  5  is  also  transmitted  wholly  polarized  in  K.  This  is  the  case 
referred  to  by  Arago  in  the  text.  From  (5.)  also  another  remarkable 
inference  follows :  if  the  reflexion  be  internal,  or  the  ray  be  incident 
on  the  second  surface  of  a  dense  medium,  we  have  r  greater  than  i, 
or 

sin  (J  —  r) 

that  is,  t\\Q  phase  of  the  reflected  vibration  is  changed  by  180°  equiva- 

•1 
lent  to  a  difference  of  —  in  route,  from  what  it  would  be  in  reflexion 

at  the  first  surface  at  the  same  incidence.     This  explains  the  sujjposed 
assunqyiion  of  the  half  undulation  in  Newton's  rings. 

Again:  if  a  polarized  ray  be  incident  on  a  reflecting  surface  with 
its  plane  of  vibrations  inclined  to  the  plane  of  incidence  (i),  at  an 
angle  (a),  its  vibration  (A)  may  be  resolved  into  two,  one  in  the  plane 
(i),  and  one  perpendicular  to  it  (k),  in  the  ratio  of  sin  a  and  cos  a, 
or  after  reflexion  we  shall  have  for  the  respective  amplitudes  (5.) 
and  (3.) 

kl  sin  a,  and  h>  cos  a. 
These  by  composition  will  give  a  resultant  ray  polarized  in  a  plane 
(p),  inclined  to  (i)  by  angle  {/3),  and  we  have  from  the  formulas  (5.) 
and  (3.) 

,       ,  .  cos  (J  +  r) 

tan  S  =■  —  tan  a --. 

cos  (i  —  /•) 


254  FRESNEL. 

ference  appear  wholly  inexplicable.     I  will  add  besides, 
that  none  of  the  partisans  of  the   system  of  emission 

This  formula  exhibits  remarkable  changes  at  successive  incidences: 
at  incidences  less  than  that  of  complete  polarization,  the  new  plane  of 
polarization  (as  indicated  by  the  sign  of  the  tangent)  deviates  on  the 
side  of  the  plane  opposite  to  that  of  polarization  (p)  —  at  (i,)  inci- 
dences c/reater,  it  deviates  on  the  same  side  as  p;  results  which  ar/ree 
exactly  with  numerous  and  accurate  observations  of  Fresnel,  Arago,  and 
Brewster. 

We  have  also  the  following  results  of  this  last  formula: 

While  a  has  any  finite  value,  when  i  =  0,  /J  =  a,  or  the  plane  of 
polarization  is  unchanged. 

When  (»■  +  ?•)  =  90°,  /:?  =  0,  or  at  the  angle  of  complete  polarization 
p  coincides  with  I. 

When  i  —  90°,  jS  =  a  again,  or  p  has  its  original  position. 

If  a  =  0,  hi  sin  a  =  0,  and  if  at  the  same  time  ( i  +  r)  —  90°,  then 
let  =  0,  or  we  also  see  that  at  the  polarizing  angle  an  incident  ray  polar- 
ized in  I  loill  cease  to  give  any  reflected  ray ;  which  agrees  with  the 
observation  originally  made  by  Malus. 

From  the  same  formulas  another  more  curious  inference  was  made 
by  Fresnel  as  follows :   In  passing  out  of  a  denser  into  a  rarer  medium, 

.     .        1 

in  general  it  is  well  known  if  t  =  90°,  sm  t  =  — . 

Consequently  a  ray  making  this  incidence  internally  on  the  bound- 
ing surface  will  not  be  refracted  out;  and  at  incidences  more  oblique 
is  experimentally  found  to  be  totally  reflected  internally :  theoretically, 
the  conversation  of  vis  viva  would  require  that  the  whole  vibratory 
force,  since  none  of  it  is  expended  on  refraction,  must  be  occupied  in 
communicating  vibrations  internally,  which  can  only  produce  internal 
waves  or  internal  total  reflexion. 

Now  at  the  critical  incidence,  in  the  formulas  for  h'  and  kt,  sin 
(i  —  r)  =  cos  i,  sin  (i  +  r)  =  sin  i  and  tan  (i  —  r)  =  cot  i  tan  {i  +  r) 
=  tan  ii;  whence  hi  =  I  and  k  =  1,  which  accords  with  total  re- 
flexion. 

At  incidences  greater  than  this  the  values  become  imaginary;  and 
by  introducing  into  them  empirically  certain  terms  i  multiplied  by 
v^^ir Fresnel  obtained  in  such  cases  an  expression  of  the  form, 

27r 

(cos  e  -\-  V— 1  sin  0)  sin  --  (vt  —  x) 

A 

1  See  Airy's  Tract,  Art.  163. 


REFLEXION    OF   POLARIZED    LIGHT.  255 

have  attempted  in  any  published  work  to  remove  the 
difficuUy,  and  it  is  not  to  be  supposed  that  they  had 
despised  it. 

And  by  the  analogy  of  certain  geometrical  cases  where  the  multi- 
plication by  -v/ — 1  indicates  a  line  differing  in  angular  position  by  90°, 
he  hazarded  the  inference  that  such  an  interpretation  might  hold 
good  here,  and  that  this  expression  would  be  equivalent  to  one  of  the 

form, 

27r  .  2/r 

cos  d  sin  -TT-  (vl  —  x)  +  sm  d  sui  —  {vi—x  +  90°; 

A  A 

which  is  trigonometrically  the  same  as 

2n-  ,  \ 


(  21"  , 


1 

This  applying  to  the  component  in  the  plane  of  incidence,  a  similar 

expression  would  apply  to  that  perpendicular  to  it, 

.     /  27r  \ 

or  sm  (  — -  (vt  —  x)  +  dl  ) 

The  difference  of  these  expressions,  or  the  relative  retardation  of 
the  two  sets  of  waves,  will  he  d  —  6'  =  6- 

In  general,  6  having  any  value,  and  the  plane  of  polarization  being 
inclined  at  an  angle  a  to  the  plane  of  incidence  on  the  rhomb,  the 
components  are, 

y  =  sin  a  sin  —  {vt  —  x  +  6)  (■*••) 

A 

z  =  cos  a  sin  —  (vt  —  x)  (*•) 

A  ^  ' 

This  then  is  precisely  the  same  case  as  that  considered  in  a  former 

note;  and  exactly  in  the  same  way  we  obtain, 

ifl  22  itiz  cos  6  .    „  „ 

~~-\ 5 : —  =  sm  2(5. 

sm  2«    cos  ^a       cos  a  sm  a 

The  general  equation  to  an  ellipse.  If  d  =  90°,  the  semi-axes  are 
sin  a  and  cos  a,  parallel  and  perpendicular  to  the  plane  of  incidence. 
If  a  =^  45°  and  6  variable,  it  is  still  an  ellipse.  If  a  =  45°  and  6  =  90°, 
it  becomes  a  circle.  Tims  a  ray  polarized  at  an  angle  a,  loith  th^  plane 
of  incidence,  after  two  internal  reflexions  in  glass,  emerges  elliptically  or 
circularly  polarized,  according  to  the  above  condition. 

From  the  empirical  terms  before  mentioned,  Fresnel  derived  ex- 
pressions from  which  he  calculated  that  for  crown  glass,  where  (i  = 
1'51,  an  internal  incidence  i  =  54°  37'  would  give  6  =  45°.  Thus 
experimentally  cutting  a  rhomb  of  such  glass  at  that  angle,  so  that 
the  ray  polarized  at  45°  to  the  plane  of  incidence,  entering  one  face 


256  FRESNEL. 

As  to  the  system  of  waves,  the  interferences  are  so 
natural  a  deduction  from  it,  that  we  have  some  reason  to 
be  astonished  that  experimenters  should  have  discovered 
them  before  theory  had  indicated  them.  To  convince 
ourselves  of  this,  it  sufi&ces  to  remark  that  a  wave,  in 
propagating  itself  through  an  elastic  medium,  communi- 
cates to  the  molecules  of  which  it  is  composed  an  oscil- 
latory motion,  in  virtue  of  which  they  displace  themselves 
successively  in  two  opposite  directions  :  this  being  under- 
stood, it  is  evident  that  a  series  of  waves  will  desti-oy 
completely  the  effect  of  another  series,  if  at  every 
point  in  the  fluid  the  motion  in  one  direction  which  the 
first  wave  produces  alone,  shall  coincide  with  the  motion 
in  the  opposite  direction  which  would  result  from  the 
sole  action  of  the  other  wave.  The  molecules  solicited 
at  the  same  time  by  equal  forces  diametrically  opposed, 
will  then  remain  at  rest,  for  as  long  a  period  as  they 
would  have  freely  oscillated  if  under  the  action  of  one 
wave  alone.  Motion  has  desti-oyed  motion  ;  now  motion 
is  light. 

I  will  not  push  further  this  enumeration,  because  we 
can  already  judge  on  how  many  points  the  antagonists  of 
the  emission  theory  have  been  successful  in  their  attacks. 
Experiments  so  numerous,  so  varied,  so  delicate,  as  those 
I  have  referred  to,  do  not  alone  testify  all  the  importance 
which  the  question  seems  to  them  to  possess  ;  they  must 

perpendicularly,  might  be  reflected  internally  at  that  angle,  and, 
passing  to  the  opposite  side,  be  reflected  again  internally  at  the  same 
angle ;  after  two  reflexions  it  would  emerge,  consisting  of  two  pencils 
polarized  at  right  angles  to  each  other,  and  having  a  difi'erence  of 
phase  6  —  90°,  and  would  thus  possess  a  circular  polarization ;  or  if 
the  inclination  was  any  other  than  45°  and  6  diftering  from  90,  the 
polarization  would  be  elliptic  of  different  degrees;  all  which  conclu- 
sions are  fully  verified  by  experiments  as  before  noticed. 


DIVERGENCE    OF   LIGHT.  257 

be  regarded  further  as  a  striking  mark  of  respect  towards 
the  great  man  whose  name,  so  to  speak,  has  been  identi- 
fied with  the  theory  which  they  think  ought  to  be  re- 
jected. As  to  the  theory  of  waves,  the  Newtonians  have 
not  done  it  the  honour  to  discuss  it  with  the  same  detail  ; 
it  has  seemed  to  them  that  a  single  objection  was  suffi- 
cient to  annihilate  it ;  and  this  objection  they  have  drawn 
from  the  manner  in  which  sound  is  propagated  in  air.  If 
light,  they  say,  is  a  vibration  like  the  vibrations  of  sound, 
it  will  be  transmitted  in  all  directions  ;  just  as  we  hear 
the  sound  of  a  distant  bell  when  we  are  separated  from  it 
by  a  screen  which  conceals  it  from  our  eyes,  in  the  same 
way  we  ought  to  perceive  the  light  of  the  sun  behind 
every  kind  of  opaque  body.  Such  are  the  terms  to 
which  we  must  reduce  the  difficulty,  for  analogy  does  not 
permit  us  to  say  that  light  ought  to  extend  itself  behind 
screens  without  losing  some  of  its  intensity  ;  since  sound 
itself,  as  every  one  knows,  does  not  penetrate  obstacles 
without  being  enfeebled  in  a  sensible  degree.  Thus,  in 
speaking  of  the  extension  of  light  into  the  geometrical 
shadow  of  a  body  as  an  insurmountable  difficulty,  New- 
ton and  his  adherents  certainly  did  not  suspect  the  answer 
which  it  would  bring  with  it ;  yet  this  answer  is  direct 
and  simple.  You  maintain  that  the  luminous  vibrations 
ought  to  extend  into  the  shadow, — they  do  so.  You  say 
that  in  the  system  of  waves,  the  shadow  of  an  opaque 
body  can  never  be  comjiletely  dark, — it  nei^er  is  so.  It 
includes  a  number  of  rays  which  give  rise  to  a  multitude 
of  curious  phenomena,  of  which  you  may  have  some 
knowledge,  since  Grimaldi  perceived  them  in  part  so 
long  ago  as  before  1633.*     Fresnel, — and  here  is  incon- 

*  Amoncf  the  earliest  difficulties  which  seemed  to  attend  the  con- 
ception of  the  wave  theory,  was  the  consideration,  which  appeared  so 


258  FRESNEL. 

testably  one  of  the  most  important  of  his  discoveries, — 
has  shown  how  and  under  what  circumstances  this  diver- 

un answerable,  that  on  this  principle  there  ought  to  be  no  darkness ; 
light  ought  to  spread  equally  into  the  shadow,  and  we  ought  to  see 
round  a  corner. 

It  was  the  fertile  principle  of  interference  which  was  to  supply  the 
answer,  as  indeed  had  been  long  before  hinted  generally  by  Huy- 
ghens.  The  waves  diverging  from  tlie  different  parts  of  a  luminous 
source  of  any  sensible  magnitude  interfere  with  and  neutralize  each 
other,  except  in  the  main  direction,  when  alone  they  exactlj'-  concur; 
— a  principle  called  "the  mutual  destruction  of  secondary  waves." 
Young  dwelt  much  at  first  on  this  objection;  and  afterwards,  in  a 
letter  to  Arago.  he  renews  a  similar  expression  of  the  difficulties  he 
felt  in  another  point  of  view:  " If  light  has  so  great  a  tendency  to 
diverge  into  the  path  of  neighbouring  rays,  and  to  interfere  with 
them,  as  Huyghens  supposed,  I  do  not  see  how  it  escapes  being  to- 
tally extinguished  in  a  very  short  space,  even  in  the  most  transparent 
medium." — Peacock's  Life,  p.  140.  But  the  principle  just  adverted 
to  shows  that  the  middle  portion  of  the  light  coming  from  a  point  of 
any  physical  magnitude  is  not  subject  to  those  mutual  interferences, 
and  does  not  diverge,  but  is  perpetually  reinforced  by  the  supply  of 
fresh  waves  incessantly  propagated  from  the  original  source.  In 
these  explanations  Young  at  length  expressed  his  full  concuiTence  in 
a  letter  to  Fresnel.  The  actual  divergence  of  light  into  a  shadow  is 
demonstrated  by  the  existence  of  the  internal  stripes.  This,  however, 
is  an  effect  only  produced  to  a  very  limited  extent;  and  the  general 
law  of  the  "mutual  destruction  of  secondary  waves"  in  ordinary 
cases  applies  to  produce  the  effect  of  destroying  all  apparent  lateral 
divergence.  There  are,  however,  some  cases  where  this  cause  operates 
less  extensively  (such,  at  least,  would  seem  to  be  the  case,  and  is  the 
view  upheld  by  some  mathematicians);  at  all  events,  under  certain 
conditions,  the  divergence  is  rendered  very  much  more  conspicuous, 
and  reaches  to  a  far  greater  distance  from  the  edge.  This  appears  to 
have  been  the  case  in  a  remarkable  experiment,  mentioned  both  by 
Newton  and  Hooke,  and  probably  observed  bj'  each  independently, 
but  described,  especially  by  Newton,  in  somewhat  obscure  terms  (see 
Optics,  book  iii.  part  i.  obs.  5,  (Ed.  1721,)  but  more  precisely  by  Hooke: 
see  Tosthumous  Works,  pp.  186  and  190,  and  plate  11,  fig.  8,  p.  155, 
Ed.  1705).  Hooke  ascribes  it  to  a  "deflexion  of  light  differing  both 
from  reflexion  and  refraction,  and  seeming  to  depend  on  the  unequal 
density  of  the  constituent  parts  of  the  ray,"  &c.     Newton  enters  ou 


DIVERGENCE    OF    LIGHT.  259 

gence  of  light  takes  place  :  he  has  further  shown  that  in 
a  complete  wave  which  is  freely  propagated,  the  rays  are 

no  theoretical  considerations  whatever,  but  mentions  it  only  among 
those  unfinished  inquiries  which,  as  he  says,  he  had  left  imperfect 
and  was  unable  to  carry  out. 

Both  the  fact,  and  all  questions  relating  to  it,  seem  to  have  been 
overlooked  until,  in  reference  to  a  somewhat  similar  case,  M.  Babinet 
supposed  that  under  particular  conditions  the  mutual  interference  of 
the  secondary  waves  might  be  interrupted  by  stopping  one  of  the  in- 
terfering portions  of  light,  and  thus  the  other  portion  be  rendered 
effective,  and  consequently  diverging  rays  made  visible.  The  author 
of  this  note,  in  relation  to  what  appears  a  closely  allied,  if  not  iden- 
tical phenomenon,  the  formation  of  a  corona  or  ring  of  light  round  the 
dark  disk  of  the  moon  in  a  total  eclipse  of  the  sun,  tried  some  analo- 
gous experiments,  and  rendered  the  same  kind  of  efifect  conspicuous 
and  easy  to  be  studied  by  an  arrangement  of  this  kind: — 

The  rays  of  the  sun  Q  are  transmitted  by  reflexion  from  an  inclined 
mirror  (in)  through  a  small  hole  {h)  in  a  shutter,  and  in  the  diverging 
beam  is  placed  an  opaque  circular  disk  (d)  which  intercepts  the  rays 
at  a  point  where  they  have  an  area  considerably  less  than  its  own  dia- 
meter. From  the  edge  of  (d)  i-ays  are  seen  to  diverge  into  its  shadow 
and  cross  at  successive  points  along  the  axis;  they  are  thus  rendered 

G 


visible  by  means  of  a  small  eye  lens  at  (e)  which  presents  the  appear- 
ance of  the  shadow  of  the  circular  disk,  having  a  multitude  of  rays 
converging  inwards  from  its  edge  to  its  centre,  where  they  form  a 
point  or  small  circle  of  great  relative  brightness.  If,  on  the  other 
hand,  the  disk  (rZ)  under  the  same  conditions  be  viewed  directhj  by 
the  eye,  without  the  lens,  its  shadow  is  seen  relatively  and  uniformly 
dark,  but  sun-ounded  by  a  bright  luminous  ring  on  its  outside.  The 
same  appearance  of  the  ring  is  also  presented  if,  instead  of  the  solar 
rays,  we  use  the  light  of  a  flame  placed  at  the  principal  focus  of  a  lens 
inserted  in  a  screen  so  as  to  send  oiit  a  beam  of  parallel  pencils  inter- 
cepted in  like  manner  by  the  disk.     In  this  case,  however,  the  con- 


260  FRESNEL. 

only  sensible  in  the  directions  which,  prolonged,  ter- 
minate in  the  luminous  points,  although  in  eacli  of  its 
successive  positions  the  different  parts  of  the  primitive 
■wave  are  in  fact  themselves  the  centres  of  disturbance, 
whence  emanate  new  waves  in  all  directions  ;  but  these 
oblique  or  secondary  waves  interfere  with  each  other, 
and  destroy  each  other  entirely.  There  remain  then 
only  the  normal  waves  ;  and  thus  the  rectilinear  propa- 
gation of  light  finds  an  explanation  in  the  system  of 
vibrations. 

"When  the  original  wave  is  not  entire,  when  it  is  broken 
or  intercepted  by  the  presence  of  an  opaque  body,  the 
result  of  the  interferences  (which  in  this  case  play  an 
important  part)  is  not  so  simple  to  explain  :  the  rays 
which  go  off  obliquely  from  all  parts  of  the  wave  not  in- 
tercepted, do  not  necessarily  destroy  each  other.  In  one 
part  they  conspire  with  the  normal  ray,  and  produce  a 
brilliant  light ;  in  another  these  same  rays  destroy  each 
other,  and  all  light  disappears.  From  the  point  where  a 
ray  is  broken,  its  propagation  is  eftected  thenceforward 
according  to  special  laws  ;  the  light  which  falls  upon  a 
screen  is  no  longer  uniform :  it  necessarily  is  composed 
of  alternate  stripes  of  brightness  and  darkness  regularly 
placed.  If  the  opaque  intercepting  body  is  not  very 
large,  the  oblique  waves  which  cross  each  other  within 

verging  rays  cannot  be  seen.  This  apparently  paradoxical  effect  has 
been  supposed  by  some  not  sufficiently  explained  on  M.  Babinet's 
principle.  The  reader  will  find  some  observations  on  the  subject,  and 
its  applications  in  the  author's  two  papers  in  the  Memoirs  of  the  Royal 
Astronomical  Society,  vol.  xvi.,  on  Luminous  Rings  round  Shadows, 
and  in  vol.  xviii.,  on  Irradiation.  Some  further  remarks  also  will  be 
found  in  his  paper  on  Lord  Brougham's  Experiments,  Phil.  Mag.  July, 
1852. —  Translator. 


AVAVE    THEORY.  2#1 

its   shadow   produce,  by  their  reciprocal   action,  stripes 
analogous  to  the  former,  but  differently  distributed. 

I  perceive  that,  without  intending  it,  in  following  the 
theoretical  speculations  of  Fresnel,  I  have  mentioned  the 
principal  features  of  those  curious  phenomena  of  diffrac- 
tion, which  I  have  before  cited  under  another  point  of 
view,  to  which  Newton  devoted  one  entire  book  of  his 
Optics.  Newton  believed  that  he  could  not  give  any  ex- 
planation of  these  phenomena  (so  difficult  did  they  seem 
to  him),  except  by  admitting  that  a  ray  of  light  cannot 
pass  close  to  a  body  without  there  undergoing  a  sinuous 
movement  like  that  of  an  eel.  In  the  explanations  of 
Fresnel  this  strange  supposition  is  superfluous. 

The  opaque  body  which  seems  to  be  the  original  cause 
of  the  diffracted  bands  does  not  act  at  all  on  the  rays, 
either  by  attraction  or  by  repulsion  ;  it  simply  intercepts 
a  part  of  the  principal  wave.  It  stops  in  the  ratio  of 
their  breadth  a  great  number  of  oblique  rays,  which,  but 
for  this  interruption,  would  have  gone  into  certain  parts 
of  space  to  mix  with  other  rays,  and  to  interfere  more  or 
less  with  them. 

Thus  it  is  no  longer  surprising  that,  as  observation  has 
proved,  the  resulting  effect  is  independent  of  the  nature 
and  mass  of  the  body.  The  periods  of  maximum  and 
minimum  of  the  light,  as  well  without  as  within  the 
shadow,  are  directly  deducible  from  the  theory  of  Fresnel 
with  a  degree  of  precision  of  which  hitherto,  perhaps,  no 
branch  of  physical  science  had  afforded  so  striking  an 
example.  Thus,  whatever  reserve  it  may  be  prudent  to 
impose  on  ourselves  when  we  run  the  risk  of  speaking 
of  the  labours  of  our  successors,  I  would  almost  venture 
to  affirm  that,  with  regard  to  diffraction,  they  will  add 
nothing  essential  to  the  discoveries  with  which  Fresnel 


262  FRESNEL. 

has  enriched  the  science.  Theories  lire,  in  general,  only 
metliods,  more  or  less  happy,  of  linking  together  a  certain 
number  of  facts  already  known.  But  when  all  the  new 
consequences  which  we  can  deduce  fi'ora  them  are  found 
to  agree  with  experience,  they  claim  a  higher  importance. 
This  kind  of  success  has  not  been  wanting  to  Fresnel. 
His  formulas  of  diffraction  include,  by  implication,  a  very 
sti-ange  result,  which  he  had  not  perceived.  One  of  our 
colleagues* — I  shall  have  no  need  to  mention  his  name, 
if  1  say  that  he  has  been  placed  long  since  among  the 
greatest  geometers  of  this  age,  as  well  by  a  multitude  of 
important  labours  in  pure  analysis,  as  by  the  most  happy 
applications  to  the  system  of  the  world,  and  to  physics, — 
perceived  at  a  glance  the  consequence  of  which  I  have 
spoken  ;  he  showed  that,  in  admitting  the  formulas  of 
Fresnel,  the  centre  of  the  shadow  of  an  opaque  and  cir- 
cular screen  ought  to  be  as  bright  as  if  the  screen  did  not 
exist.  This  consequence,  apparently  so  paradoxical,  was 
subjected  to  trial  by  direct  experiment,  and  observation 
has  perfectly  confirmed  the  result  of  calculation. 

In  the  long  and  difficult  discussion  to  which  the  nature 
of  light  has  given  birth,  and  of  which  I  have  just  traced 
the  history,  the  task  of  the  physicists  has  been  nearly  ful- 
filled ;  as  to  that  of  the  mathematicians,  it  unhappily  still 
offers  some  deficiencies  to  be  filled  up.  I  would  venture 
then,  if  I  had  the  right,  to  adjure  that  great  geometer 
to  whom  optical  science  owes  the  important  result  just 
mentioned,  to  try  whether  the  half  empirical  formulas  by 
which  Fresnel  has  attempted  to  express  the  intensities 
of  light  reflected  under  all  angles  and  for  all  kinds  of 
surfaces,  may  not  be  found  deducible  also  from  the  gen- 
eral equations  of  motion  of  elastic  fluids.  It  remains, 
*  Poisson, 


LIGHT-HOUSES.  263 

above  all,  to  explain  how  the  difFererit  undulations  can 
undergo  unequal  deviations  at  the  bounding  t^urfaces  of 
transparent  bodies. 

LIGHT-HOUSES. 

In  an  academy  of  sciences,  if  it  properly  appreciate  its 
functions,  the  author  of  a  discovery  is  never  exposed  to 
the  discouraging  question  so  often  addressed  to  him  in 
the  world,  of  cui  bono  ?  Here  every  one  comprehends 
that  the  animal  life  ought  not  to  be  the  sole  occupation  of 
man  ;  that  the  cultivation  of  his  intellect, — that  an  atten- 
tive study  of  this  infinite  variety  of  animated  beings,  and 
inert  matter,  with  which  he  is  surrounded,  forms  the  most 
beautiful  portion  of  his  destined  pursuits. 

But  besides,  even  if  we  were  desirous  to  find  nothing 
in  the  sciences  but  the  means  of  facilitating  the  reproduc- 
tion of  substances  for  food, — of  weaving  with  more  or  less 
economy  and  perfection  the  different  fabrics  which  serve 
for  clothing, — of  constructing  with  elegance  and  solidity 
the  convenient  habitations  in  which  we  escape  the  vicis- 
situdes of  the  seasons, — of  extracting  from  the  bowels  of 
the  earth  so  many  metals  and  combustible  matter,  which 
are  necessary  for  the  arts  of  life, — of  annihilating  a  hun- 
dred material  obstacles  which  oppose  themselves  to  the 
intercommunication  of  inhabitants  of  the  same  continent, 
of  the  same  kingdom,  even  of  the  same  city, — of  extract- 
ing and  preparing  the  medicaments  proper  for  combating 
the  numerous  disorders  with  which  our  organs  are  inces- 
santly threatened, — the  question  of  cui  bono  2  will  be 
found  completely  announced.  Natural  phenomena  have 
innumerable  points  of  connection  with  each  other,  often 
hidden,  the  discovery  of  which  one  age  bequeathes  to 
another.     At  the  moment  when  these  relations  ai'e  dis- 


264  FEESNEL. 


covered,  important  applications  rise  up,  as  if  by  enchant- 
ment, out  of  experiments  wliich,  until  then,  would  seem 
likely  to  remain  for  ever  among  the  number  of  abstract 
speculations.     A  fact  which  no  direct  utility  had  as  yet 
recommended  to  the  attention  of  the  public  becomes,  per- 
haps, the  step  on  which  a  man  of  genius  supports  himself 
to  climb  up  to  those  primary  truths  which  change  the 
■whole  face  of  science,  whether  for  creation  of  some  eco- 
nomical moving  power,  which  all  manufacturing  arts  will 
henceforth  adopt,  and  of  which  not  the  least  merit  is  that 
of  delivering  thousands  of  operatives  from  overwhelming 
toils  which  assimilated  them  with  the  brutes,  ruined  their 
health,  and  brought  them  to  a  premature  death.     If  to 
fortify  these  reflections  examples  may  be  thought  neces- 
sary, I  should  feel  no  other  embarrassment  than  that  of 
too  wide  a  choice.      But  here  there  is  no  necessity  to 
enter  on  such  details  ;  for  to  all  the  theoretical  researches 
already  mentioned,  Fresnel  has  added  an  important  labour, 
having  an  immediate  practical  application,  which  will  cer- 
tainly place  his  name  among  those  of  the  benefactors  of 
the  human  race.     This  work,  every  one  knows,  had  for 
its  object  the  improvement  of  light- houses.     I  will  pro- 
ceed to  trace  the  outline  of  its  progress,  and  shall  thus 
have  finished  the  sketch  which  I  proposed  to  offer  you  of 
the  brilliant  scientific  career  of  our  late  colleague. 

Persons  unacquainted  with  nautical  matters  are  usually 
seized  with  a  sort  of  fear  when  the  vessel  which  carries 
them,  at  a  distance  from  continents  or  islands,  has  no 
other  witness  of  its  progress  than  the  stars  and  the  waves. 
A  view  of  any  coast  the  most  barren,  the  most  rocky,  the 
most  inhospitable,  dissipates,  as  if  by  enchantment,  those 
undefined  fears  which  their  absolutely  isolated  position 
had  inspired,  while,  to  the  experienced  navigator,  it  is 


LIGHT-HOUSES.  265 

near  the  land  alone  that  the  dangers  are  seen  to  com- 
mence. 

Such  danger  occurs  in  ports  into  which  no  prudent 
sailor  would  enter  without  a  pilot ;  it  occurs  where,  even 
with  this  help,  no  one  would  risk  attempting  to  penetrate 
at  night ;  we  easily  see,  then,  how  indispensable  it  is,  if 
we  would  avoid  irreparable  accidents,  that  after  sunset 
signals  of  flame,  easily  visible,  should  indicate  on  all  sides 
the  proximity  of  land.  It  is  necessary  moreover  that 
every  ship  should  perceive  the  signal  far  enough  off  for  it 
to  find,  in  evolutions  often  sufBciently  difRcult,  the  means 
of  keeping  itself  at  some  distance  from  the  shore  until  the 
moment  when  day  shall  appear.  It  is  not  less  desirable 
that  the  different  lights  which  we  kindle  along  a  certain 
extent  of  coast  should  not  be  confounded  with  each  other ; 
and  that  at  first  sight  of  these  hospitable  signals  the  navi- 
gator, who  by  an  unfavourable  sky  has  been  for  some 
days  deprived  of  the  means  of  directing  his  course,  should 
know,  for  example,  on  returning  from  America,  whether 
he  is  about  to  enter  the  Gironde,  the  Loire,  or  the  har- 
bour of  Brest. 

On  account  of  the  roundness  of  the  earth,  the  range  of 
a  light-house  depends  on  its  height.  In  this  respect  men 
have  always  obtained  without  difficulty  the  range  which 
the  wants  of  navigation  demanded  :  it  was  a  simple  ques- 
tion of  expense  ;  every  one  knows,  for  instance,  that  the 
great  edifice  with  which  the  famous  architect  Sostrates 
of  Cnidus  adorned  the  harbour  of  Alexandria,  nearly 
three  hundred  years  before  our  era,  and  most  of  the 
light-houses  constructed  by  the  Romans,  were  of  consid- 
erably greater  height  than  the  most  celebrated  modern 
towers.     But  in  an  optical   point  of  view,  these  light- 

SEC.    SEE.  12 


266  FRESNEL. 

houses  were  but  little  remarkable  ;  the  feeble  rays  which 
proceeded  from  fires  of  wood  or  of  coal,  lighted  in  the 
open  air  on  their  summits,  could  never  penetrate  the 
thick  vapours  which  in  all  climates  obscure  the  lower 
regions  of  the  atmosphere. 

Nevertheless,  as  to  the  intensity  of  light,  the  modern 
light-houses  were  but  little  superior  to  the  ancient.  The 
first  important  amelioration  which  they  received,  dates 
from  the' double-current  lamp  of  Argand  ;  that  admirable 
invention  which  would  be  much  better  appreciated,  if, 
while  our  museums  include  works  of  the  period  of  the 
decline  of  art  in  a  i)urely  historical  point  of  view,  the  re- 
positories of  industi'ial  science  presented  successively  to 
public  inspection  the  various  means  of  illumination,  so 
dull,  so  bad,  so  ill-suited,  so  nauseous,  which  were  em- 
ployed only  fifty  years  ago,  by  the  side  of  those  elegant 
lamps  whose  pure  and  brilliant  light  rivals  that  of  a  sum- 
mer day. 

Four  or  five  Argand  lamps  united,  would  give  without 
doubt  as  much  light  as  the  large  fires  which  the  Romans 
used  with  so  much  trouble,  on  the  lofty  towers  of  Alexan- 
dria of  Puzzuoli,  or  of  Ravenna  ;  but  in  combining  these 
lamps  with  reflecting  mirrors,  their  natural  effects  may 
be  prodigiously  increased.  The  principle  of  this  last  in- 
vention ought  to  arrest  our  attention  for  an  instant, 
because  it  will  enable  us  rightly  to  appreciate  the  value 
of  Fresnel's  labour. 

The  light  of  a  burning  body  expands  uniformly  in  all 
directions, — one  part  falls  on  the  ground,  and  is  lost ; 
another  portion  ascends,  and  is  dissipated  in  space  ;  the 
sailor  whose  route  we  wish  to  enlighten,  profits  only  by 
those  rays  which  are  emitted  horizontally,  or  nearly  so, 
from  the  lamp  across  the  sea  ;  all  the  rays,  even  those 


SUCCESSIVE    IMPROVEMENTS.  267 

which  are  horizontal,  directed  towards  the  land,  have 
only  been  produced  to  be  entirely  wasted. 

This  horizontal  beam  of  rays  not  only  forms  a  very 
small  part  of  the  total  light ;  it  has  also  the  serious  incon- 
venience of  diminishing  in  intensity  as  it  diverges,  and  of 
not  extending  itself  to  a  distance  without  being  sensibly 
enfeebled.  To  destroy  this  unfortunate  loss  of  light, — to 
profit  by  all  the  light  which  the  lamp  emits, — was  the 
twofold  problem  which  remained  to  be  resolved  in  order 
to  extend  the  range,  and  thus  the  utility,  of  light-houses. 
Concave  metallic  mirrors,  called  parabolic  reflectors, 
have  furnished  a  satisfactory  solution. 

When  the  lamp  is  jilaced  at  the  focus  of  such  a  mirror, 
all  the  rays  which  emanate  from  it  are  brought,  by  the 
reflexion  they  undergo  against  its  sides,  into  a  common 
direction  ;  their  original  divergence  is  destroyed  ;  they 
form,  as  they  issue  from  the  apparatus,  a  cylinder  of  light 
parallel  to  the  axis  of  the  mirror.  This  beam  is  trans- 
mitted to  the  greatest  distances  with  the  same  brightness, 
except  that  the  atmosphere  absorbs  a  small  part  of  it. 

Before  proceeding  further,  let  us  stop  to  observe  that 
this  construction  is  not  without  an  inconvenience.  We 
thus  indeed  easily  bring  to  bear  on  the  horizon  of  the  sea 
a  multitude  of  rays  which  would  otherwise  have  been  lost 
on  the  ground,  in  space  above,  or  on  the  side  towards  the 
land  ;  and  we  overcome  the  divergence  of  those  rays 
which  would  naturally  be  directed  towards  the  navigator. 
But  the  cylinder  of  reflected  rays  can  have  no  greater 
breadth  than  that  of  the  mirror ;  the  space  which  it  illu- 
minates has  precisely  the  same  breadth  at  all  distances  ; 
unless  indeed  we  employed  many  similar  mirrors,  pointed 
different  ways,  and  even  then  the  hoi-izon  would  include 
many  large  spaces  completely  dark,  in  which  the  pilot 


268  FRESNEL. 

would  perceive  no  signal.  This  great  evil  is  overcome 
by  giving,  by  means  of  clockwork,  an  uniform  motion  of 
rotation  to  the  reflector.  The  luminous  beam  issuing 
from  this  mirror  is  then  successively  directed  to  all  points 
of  the  horizon  ;  every  ship  sees  the  light  at  one  instant 
appear,  and  at  another  disappear ;  and  if  in  a  great  length 
of  coast,  as  for  example  from  Brest  to  Bayonne,  there  do 
not  exist  any  two  light-houses  with  the  same  period  of 
rotation,  all  the  signals  are,  so  to  speak,  individualized. 
According  to  the  interval  which  elapses  between  two 
appearances  or  two  eclipses  of  the  light,  the  navigator 
always  knows  what  point  of  the  coast  is  in  vi5w ;  he  finds 
himself  no  longer  liable  to  mistake  the  light-house  for  a 
planet  or  star  of  the  first  magnitude  near  to  it  rising  or 
settino',  or  even  for  those  accidental  fires,  kindled  on  the 
coast  by  fishermen,  woodcutters,  or  charcoal  burners, — 
fatal  mistakes  which  have  often  been  the  cause  of  deplor- 
able shipwrecks. 

A  transparent  lens  brings  to  parallelism  all  the  lumi- 
nous rays  which  traverse  it,  whatever  might  be  their 
original  degree  of  divergence,  provided  the  point  from 
which  the  rays  diverge  be  coincident  with  that  point  be- 
longing to  the  lens  which  we  call  its  focus.  Glass  lenses, 
then,  may  be  substituted  for  mirrors,  and  in  fact  a  light- 
house with  lenses  has  been  long  ago  executed  in  England 
under  the  idea,  at  first  sight  very  plausible,  that  it  would 
be  much  more  brilliant  than  light-houses  with  reflectors. 
Yet  it  was  found  in  practice  that  mirrors,  notwithstand- 
ing the  gross  loss  of  light  which  they  produce  at  their 
surface  in  the  act  of  reflexion,  direct  to  the  horizon  a 
more  intense  beam  of  light.  Lenses  were  therefore  aban- 
doned. 

The  unknown  author  of  this  abortive  attempt  proceeded 


LENSES    FOR    LIGHT-HOUSES.  269 

at  hazard.  In  occupying  himself  with  the  same  problem, 
Fresnel,  with  his  habitual  penetration,  perceived  at  the 
first  glance  where  the  difficulty  lay.  He  saw  that  the 
lenticular  light-houses  could  only  become  superior  to 
those  with  reflectors,  by  increasing  considerably  the  in- 
tensity of  the  flame  which  supplied  the  illumination  ; 
or  by  giving  to  the  lenses  enormous  dimensions  which 
seemed  to  surpass  all  that  any  ordinary  work  could  ac- 
complish. He  observed  also  that  the  lenses  must  have 
a  very  short  focal  length ;  that,  in  making  them  according 
to  the  usual  forms,  they  had  too  great  a  thickness,  too 
small  a  transparency  ;  and  that  their  weights  were  consid- 
erable, and  pressed  too  much  on  the  machinery  for  making 
them  rotate,  so  as  speedily  to  bring  on  its  destruction. 

To  avoid  this  excessive  thickness  of  the  ordinary  lenses, 
their  enormous  weight,  and  want  of  transparency,  which 
were  its  consequences,  they  were  replaced  by  others  of  a 
peculiar  form,  which  Buffbn  had  imagined  for  another 
purpose,  and  which  he  called  lenses  by  steps.  (Lentilles 
a  echelons.)*     It  is  possible  at  the  present  day  to  con- 

*  The  nature  of  these  lenses  a  echelons  will  be  understood  at  once 
from  the  annexed  sketch,  where  this  construction  is  represented  in 
front  view  and  in  section.     The  effect  of  one  continuous  lens  is  made 


up  by  a  combination  of  separate  pieces,  instead  of  one  large  lens  as 
indicated  by  the  dotted  outline. — See  Brewster's  Optics.  Cab.  Cyclop, 
p.  322. 


270  FBESNEL. 

struct  the  largest  lenses  of  this  kind,  although  we  do  not 
yet  know  how  to  fabricate  thick  masses  of  glass  free  from 
defects.  It  suffices  to  compose  them  of  a  number  of  dis- 
tinct small  pieces  ;  a  plan  proposed  by  Condorcet. 

I  can  here  affirm  that,  at  the  moment  when  the  idea  of 
these  lenses  "  by  steps  "  occurred  to  the  mind  of  Fresnel, 
he  had  not  the  least  knowledge  of  the  previous  projects 
of  Buffisn  and  Condorcet.  But  assertions  of  this  kind 
are  interesting  only  to  the  author  in  regard  to  his  own 
claims,  they  have  no  value  for  the  public.  In  its  eyes 
there  is  not, — I  will  say  more,  there  ought  not  to  be 
more  than  one  inventor, — he  who  first  makes  public  the 
discovery.  After  so  large  a  concession,  it  may  at  least 
be  allowed  me  to  remark  that  in  1820  there  did  not 
exist  a  single  lens  of  this  construction  in  the  physical 
cabinets,  and  that  besides,  up  to  that  time,  lenses  had 
only  been  regarded  as  the  means  of  producing  great 
effects  of  heat ;  that  it  was  Fresnel  who  created  methods 
to  construct  them  with  exactness  and  economy  ;  that  it 
was  he,  and  he  alone,  who  even  imagined  the  application 
of  them  to  light-houses.  This  application,  however  (as  I 
have  just  pointed  out),  could  never  have  led  to  any  use- 
ful result  if  it  had  not  been  combined  with  suitable  modi- 
fications of  the  lamp  ;  if  the  illuminating  power  of  flame 
had  not  been  greatly  augmented.  This  important  part  of 
the  system  required  special  studies,  numerous  and  deli- 
cate experiments.  Fresnel  and  one  of  his  friends  (Arago) 
devoted  themselves  to  the  inquiry  with  ardour  ;  and  their 
common  labour  led  to  the  construction  of  a  lamp  with 
many  concentric  wicks,  whose  brilliancy  was  twenty-five 
times  that  of  the  best  lamps,  with  only  a  double  current. 

In  the  glass  lenses  imagined  by  Fresnel,  each  lens 
sent  successively  to  all  parts  of  the  horizon  a  light  equiv- 


LENSES    FOR    LIGHT-HOUSES.  271 

alent  to  that  of  3,000  or  4,000  Avgand  lamps  united  ; 
that  is,  eight  times  that  produced  by  the  beautiful  sil- 
vered parabolic  reflectors  of  which  our  neighbours  make 
use  ;  it  is  also  equivalent  to  the  light  which  we  should 
obtain  by  uniting  in  one  the  third  part  of  the  total 
quantity  of  the  gas-lights  which  illuminate  the  streets, 
the  shops,  and  the  theatres  of  Paris.  Such  a  result  does 
not  seem  devoid  of  importance,  if  we  remark  that  it  is 
obtained  with  a  single  lamp.  In  perceiving  such  power- 
ful effects,  the  Government  took  care  to  authorize  Fres- 
nel  to  cause  to  be  constructed  one  of  his  instruments, 
and  selected  the  lofty  Tower  of  Cordouan,  at  the  mouth 
of  the  Gironde,  as  the  point  where  it  should  be  placed. 
The  new  light-house  was  at  length  constructed  in  the 
month  of  July,  1823. 

The  light-house  of  Fresnel  has  since  had  for  judges, 
during  seven  consecutive  years,  the  multitude  of  mari- 
ners of  all  countries  who  frequent  the  Gulf  of  Gascony. 
It  was  also  studied  assiduously  at  the  place  by  skilful 
engineers,  who  came  expressly  from  the  north  of  Scot- 
land with  a  special  mission  from  the  British  Govern- 
ment. I  shall  here  be  the  interpreter  of  the  opinions 
both  of  the  one  and  the  othei-,  when  I  affirm  that  France, 
since  there  the  important  invention  of  revolving  lights 
had  its  origin,  possesses,  thanks  to  the  labours  of  our 
scientific  colleague,  the  most  beautiful  light-houses  in  the 
world.  It  is  always  glorious  to  march  at  the  head  of  the 
sciences  ;  but  we  experience  above  all  a  lively  satisfac- 
tion in  claiming  the  first  rank  for  our  country,  when  the 
question  relates  to  one  of  those  happy  applications  in 
which  all  nations  are  called  upon  to  take  an  equal  part, 
and  of  which  humanity  will  never  have  occasion  to  com- 
plain. 


272  FRESNEL. 

There  exist  at  present  on  the  ocean  and  on  the  Medi- 
terranean twelve  light-houses,  more  or  less  powerful,  con- 
structed on  the  principles  of  Fresnel.  To  complete  the 
general  system  of  lighting  our  coasts,  thirty  new  light- 
houses appear  still  necessary.  Every  thing  induces  us 
to  hope  that  these  important  works  will  be  promptly 
executed,  and  that  we  shall  deviate  in  the  least  possible 
degree  from  the  happy  direction  given  to  this  branch  of 
the  public  service  by  our  colleague.  Routine  and  pi'eju- 
dice  will  here  be  without  power,  since  the  parties  inter- 
ested who  are  the  true  judges,  the  mariners  of  all 
nations,  have  unanimously  proclaimed  the  superiority  of 
the  new  system.  No  one  can  allege  pretexts  of  economy, 
for  to  produce  equal  etfect,  the  lenticular  light-houses  do 
not  require  so  much  oil  as  those  of  the  old  construction  ; 
are  of  a  much  less  expensive  kind  to  keep  up,  and  pro- 
cure definitively  to  the  state  an  annual  economy  of  about 
half  a  million.  This  beautiful  invention,  then,  ought  to 
prosper  at  least,  if  since  the  death  of  Fresnel  it  did  not 
fall  into  the  hands  of  those  persons,  strangers  to  the  sub- 
ject, who  think  themselves  fit  for  all  employments, 
although,  under  different  states  of  public  affairs,  they 
have  had  no  other  places  of  study  than  the  antechambers 
of  ministers.  Candidates,  if  I  am  rightly  informed,  were 
not  wanting ;  but  happily,  this  time,  intrigue  yielded  to 
merit,  and  the  chief  superintendence  of  the  light-liouses 
was  intrusted  to  the  younger  brother  of  Fresnel,  like 
himself  a  former  pupil  of  the  Ecole  Polytechnique,  like 
himself  an  engineer  of  the  "  ponts  et  chausees," — skilful, 
zealous,  and  conscientious. 

Under  his  inspection,  the  construction  and  the  dispo- 
sition of  great  lenses  "  in  steps  "  has  received  important 
improvements,  and  the  public  will  not  have  to  fear  that 


EXAMINER    IN    THE    ECOLE    POLYTECHNIQUE.      273 

any  negligence  will  deprive  these  beautiful  instruments 
of  any  part  of  their  power.  Such  inheritances  of  national 
glory  will  surely  never  be  allowed  to  suffer  neglect. 

LIFE    AND    CHARACTER    OF    FRESNEL. HIS    DEATH. 

The  numerous  discoveries  which  I  have  just  described 
were  all  made  in  the  .short  interval  between  1815  and  1826, 
without  occasioning  any  neglect  of  the  duties  confided  to 
Fresnel,  either  as  engineer  of  the  pavements  of  Paris,  or 
as  secretary  of  the  commission  of  light-houses.  But  our 
colleague,  at  the  same  time,  entirely  withdrew  from  the 
temptations  to  idleness,  which  abound  more  in  Paris  than 
any  other  city,  and  which  those  who  yield  themselves  to 
them  call  the  duties  of  society,  in  order  to  appease  their 
consciences,  and  to  explain  to  themselves  how  their  time 
is  so  ill  employed.  A  life  in  the  study,  a  life  altogether 
intellectual,  however,  was  but  ill  suited  to  the  frail  con- 
stitution of  Fresnel.  However,  the  anxious  cares  of  his 
estimable  family  were  abundantly  bestowed  on  him  ; — 
the  thoroughly  contented  disposition  of  this  simple- 
minded  man,  than  whom  no  one  ever  better  deserved 
the  title,  reacted  powerfully  in  preserving  his  health  ; — 
and  lastly,  his  extreme  temperance  led  to  the  hope  that 
he  might  be  long  spared  to  the  sciences. 

The  emoluments  of  the  two  offices  held  by  Fresnel, 
that  of  engineer  and  academician,  would  have  amply 
sufficed  for  his  moderate  desires,  if  the  craving  for  scien- 
tific research  had  not  been  with  him  a  second  nature. 
The  construction  and  purchase  of  those  delicate  instru- 
ments, without  which,  at  the  present  day,  we  cannot  pro- 
duce any  thing  exact  in  physics,  absorbed  every  year  a 
considerable  part  of  his  fortune.  He,  therefore,  was 
anxious  to  create  new  resources.     The  situation,  so  very 

12* 


274  FRESNEL . 

moderately  remunerated,  of  temporary  examiner  of  the 
pupils  at  the  Ecole  Poly  technique  offered  itself;  Fresnel 
obtained  it ;  but  his  friends  were  not  slow  to  perceive 
that  he  had  presumed  too  much  on  the  powers  of  his 
constitution  ;  that  the  ardour  Avith  which  he  fulfilled  his 
new  duties  and  the  anxieties  he  felt, — in  fact  unduly  ex- 
aggerated,— in  classing  the  candidates  in  the  order  of 
merit,  seriously  affected  his  health,  already  so  precarious ; 
and  yet,  how  could  they  advise  a  resignation,  of  which 
the  inevitable  result  would  be  the  abandonment  of  many 
glorious  labours  ?  Under  these  circumstances,  one  of 
the  most  desirable  scientific  offices,  among  all  those  of 
which  the  government  has  the  disposal,  that  of  examiner 
of  the  pupils  in  navigation,  became  vacant.  This  office 
requires  only  moderate  labour.  The  annual  journey 
which  it  involves  was,  in  the  eyes  of  his  medical  advisers, 
a  reason  why  it  should  be  more  desirable  that  Fresnel 
should  obtain  it.  He  determined,  therefore,  to  become  a 
candidate  ;  as  every  one  would  believe,  there  is  no  im- 
propriety in  asking  for  an  employment,  for  which  long 
studies  peculiarly  qualify  a  person,  and  which  he  could 
conscientiously  fulfil.  Literary  men  suppose  that  after 
undertaking  toilsome  labours  they  can,  without  reproach, 
aspire  to  the  enjoyment  in  their  old  age  of  that  inde- 
pendence which  the  most  inconsiderable  artisan  in  Paris 
is  sure  of  obtaining  one  day,  however  slight  may  be  his 
labours  or  inferior  his  rank.  No  one  has  ever  main- 
tained that  there  is  not  both  jjropriety  and  advantage  in 
every  case  in  choosing  the  most  worthy.  The  glory 
which  such  men  as  Lagrange,  Laplace,  Legendre,  re- 
flected on  the  board  of  longitude  and  on  the  Academy, 
seemed  to  associate  itself  with  the  eminent  services 
which,  under  other  other  titles,  these   illustrious  geom- 


EXAMINER    IN    THE    ECOLE    POLTTECHNIQUE.      275 

eters  had  rendered  to  the  Ecole  Polytechnique.  In  the 
public  courses,  the  pupils  claim  that  the  professors  should 
be  earnest,  lucid,  and  methodical ;  but  it  is  no  concern 
of  theirs  to  inquire  whether  other  audiences  in  other 
establishments  receive  instruction  from  the  same  men. 
The  sciences  will  not  appear  an  idle  supertluity  ;  and  we 
may  admit  that  Papin,  in  inventing  the  steam-engine  ; 
Pascal,  in  pointing  out  the  principle  of  the  hydraulic 
press  ;  Lebon,  in  imagining  lighting  by  gas  ;  Berthollet, 
in  inventing  bleaching  by  chlorine  ;  Leblanc  in  teaching 
us  to  extract  from  sea-water  the  soda  which  formerly  had 
to  be  imported  at  high  prices ;  have  nobly  paid  to  soci- 
ety the  debt  of  science. 

If  we  ought  to  believe  some  persons,  whose  intentions 
I  would  rather  commend  than  their  enlightenment,  I 
should  have  to  enumerate  a  long  series  of  prejudices,  and 
should  have  to  defend  the  author  of  so  many  beautiful 
discoveries,  the  originator  of  a  new  system  of  light- 
houses, the  man  of  science  whose  name  navigators  will 
eternally  bless,  from  the  charge  of  having  desired,  by  the 
union  of  two  otfices,  to  procure  for  himself  an  annual 
life-income  of  12,000  francs,  of  which  the  greatest  part 
would  certainly  have  been  devoted  to  the  expenses  of 
new  researches.  The  defence  of  our  colleague  would, 
without  doubt,  be  an  easy  task  ;  but  I  may  omit  it ; 
Fresnel  did  not  obtain  the  employment  he  sought,  and 
that  from  causes  which  I  would  willingly  pass  over  in 
silence,  if  they  were  not  such  as  to  give  me  occasion  for 
showing  that  men  of  letters, — whose  character  there 
have  recently  been  attempts  to  dishonour,  by  represent- 
ing them  as  harpies  rushing  without  rule  or  moderation 
to  prey  upon  the  public  purse, — know  well  how  to 
renounce   nobly   the  most   desirable  offices,  even  those 


276  FRESNEL. 

which  they  might  claim  as  a  sacred  debt,  as  soon  as 
their  dignity  would  become  compromised. 

I  have  ah-eady  mentioned  how  much  the  duties  of 
examiner  at  the  Ecole  Polytechnique  endangered  the 
health  of  Fresnel ;  how  desirable  it  became  that  his  wish 
for  a  less  laborious  situation  should  be  attained.  The 
incontestable  superiority  of  his  scientific  claims,  the  with- 
drawal of  all  competitors,  the  behaviour  of  one  of  our 
honourable  colleagues,  one  of  the  first  geometers  of  the 
age  ;  and  lastly,  the  active  conduct  of  M.  Becquey, 
who,  on  every  occasion,  treated  Fresnel  with  the  kind- 
ness of  a  father,  had  smoothed  over  many  obstacles. 
The  minister  on  whose  decision  the  appointment  de- 
pended had  himself,  during  his  youth,  been  occupied 
with  the  study  of  the  sciences  in  a  distinguished  degi-ee  ; 
he  had  even  kept  up  the  taste  for  them ;  he  desired  to 
see  our  colleague,  and  from  that  moment  his  nomination 
seemed  sure  ;  for  the  reserved  manner  of  Fresnel,  the 
sweetness  of  his  character,  the  unaffected  modesty  of  his 
language,  conciliated  instantly  the  goodwill  even  of  those 
who  did  not  understand  his  works  ;  but,  alas,  in  the  train 
of  civil  discords,  to  how  many  mistakes  are  we  not  ex- 
posed, if  we  proceed  to  judge  of  that  which  will  be  from 
that  which  ought  to  be.  How  many  little  circumstances, 
paltry  interests,  heterogeneous  elements,  come  in  and 
mix  themselves  with  affairs  the  most  simple,  and  prevail 
over  rights  the  most  incontestable.  For  my  own  part,  I 
cannot  say  on  what  occasion  the  Minister  of  the  Interior, 
addressing  himself  to  the  royalist  volunteer  of  the  Drome, 
put  the  following  question,  clearly  intimating  that  his 
nomination  depended  on  the  answer  he  gave  :  "  Sir,  are 
you  truly  on  our  side  ? "  "  If  I  understand  rightly, 
Monseigneur,  I  should   answer  that  there  exists  no  one 


POLITICAL    INFLUENCES.  277 

more  devoted  than  myself  to  the  august  family  of  our 
kings,  and  to  the  wise  institutions  which  France  owes  to 
it."  "  All  this,  sir,  is  too  vague  ;  we  shall  understand 
one  another  better  by  using  plain  terms.  If  you  were  a 
deputy,  by  the  side  of  which  member  would  you  sit  ?  " 
"  Monseigneur,"  replied  Fresnel,  without  hesitation,  "  by 
the  side  of  Camille  Jordan,  if  I  were  worthy."  "  Many 
thanks  for  your  frankness,"  replied  the  minister.  The 
next  day  an  unknown  individual  was  named  examiner 
of  the  marine. 

Fresnel  received  this  repulse  without  a  word  of  com- 
plaint. In  his  mind,  the  personal  question  was  entirely 
effaced  in  comparison  with  the  pain  he  felt  in  seeing, 
after  thirty  years  of  debates  and  troubles,  political  pas- 
sions still  so  little  subdued.  When  a  minister,  whose 
private  qualities  might  claim  the  homage  of  good  men  of 
all  parties,  considered  himself  obliged  to  ask  a  scientific 
examiner,  not  for  proofs  of  incorruptibility,  of  zeal,  or  of 
knowledge,  but  for  an  assurance  that,  if  by  chance  he 
should  ever  happen  to  become  a  deputy,  he  would  not 
determine  to  sit  at  the  side  of  Camille  Jordan,  a  good 
citizen  could  not  but  fear  that  our  political  futui'e  was  not 
to  be  exempt  from  storms. 

The  body  of  instructors  of  the  Ecole  Polytechnique, 
under  all  regimens,  has  suffered  little  from  political  influ- 
ences. There  the  examiner  and  the  professor  must  daily 
discharge  their  duties  in  person  ;  there,  under  the  eyes 
of  a  nursery  of  skilful  hearers,  and  in  some  slight  degree 
inclined  to  malice,  inaccurate  refinements,  false  calcula- 
tions, bad  experiments  in  chemistry  or  physics  would  in 
vain  seek  refuge  under  the  shelter  of  the  opinions  of  the 
day.  Fresnel  might  then  hope  that,  notwithstanding  his 
recent  profession  of  faith,  they  would  not  deprive  him  of 


278  FRESNEL. 

the  place  of  temporary  examiner.  Besides,  this  office  is 
extremely  laborious,  and  experience  has  sufficiently 
shown,  that  sinecures  are  the  places  sought  after  with 
more  especial  ardour.  Fresnel  then  continued  his  former 
functions:  but  at  the  close  of  the  examination  of  1824, 
an  attack  of  hemoptysis  forced  him  to  retire  from  his 
labours,  and  caused  the  most  serious  alarm  to  his  friends. 
From  this  moment  our  unfortunate  colleague  was  obliged 
to  abandon  every  scientific  research  which  required  close 
attention,  and  to  devote  solely  to  the  business  of  the  light- 
houses the  few  moments  of  relief  which  his  malady  left 
him.  The  most  tender  and  marked  attentions  soon  be- 
came powerless  against  the  rapid  progress  of  the  disease. 
It  Avas  then  resolved  to  try  the  effects  of  country  air ; 
alas  !  but  a  too  evident  indication  of  the  little  hope  enter- 
tained by  the  skilful  physician  in  whom  Fresnel  confided. 
However,  not  to  distress  his  family,  our  unfortunate  col- 
league affected  to  entertain  hope,  and  at  the  beginning  of 
June,  1827,  he  was  removed  to  Ville  d'Avray.  There 
he  saw  the  approach  of  death  with  the  calmness  and  re- 
signation of  a  man  whose  whole  conduct  had  been  without 
reproach.  A  young  engineer  of  high  distinction,  M.  Du- 
leau,  found,  in  the  lively  friendship  which  united  him  to 
our  colleague,  an  irresistible  impulse  to  take  part  in  the 
melancholy  kind  offices  of  which  he  was  the  object ;  and 
he  also  established  himself  at  Ville  d'Avray.  M.  Duleau 
was  the  first  who  informed  us  how  little  Fresnel  was 
under  any  delusion  as  to  his  condition.  "  I  could  have 
wished,"  lie  exclaimed  sometimes  (when  the  presence  of 
a  mother  and  a  brother,  who  were  agitated  by  poignant 
disquietude,  did  not  impose  upon  him  a  reserve  which  his 
tender  feelings  for  them  would  not  infringe),  "I  could 
have  wished  to  live  longer,  because  T  perceive  that  there 


DEATH    OF    FRESNKL.  279 

are  in  the  inexhaustible  range  of  science,  a  great  number 
of  questions  of  public  utility,  of  which,  perhaps,  I  might 
have  had  the  happiness  of  finding  the  solution."  Fresnel 
was  still  in  the  country  Avhen  the  Royal  Society  of  Lon- 
don charged  me  with  the  office  of  presenting  to  him  the 
Ruraford  Medal.  His  powers,  then  almost  exhausted, 
scarcely  permitted  him  to  cast  a  glance  of  his  eye  over 
this  testimony,  so  rarely  bestowed,  of  the  estimation  of 
that  illustrious  society.  All  his  thoughts  were  directed 
towards  his  approaching  end  :  all  were  concentrated  on 
that  object.  "  I  thank  you,"  he  said  to  me,  in  a  feeble 
voice,  "for  having  undertaken  this  mission.  I  guess  how 
much  it  must  have  cost  you,  for  you  have  perceived,  is  it 
not  so  ?  that  the  most  beautiful  crown  is  worth  little  when 
it  is  only  to  be  deposited  on  the  tomb  of  a  friend  ! " 

Alas  !  these  melancholy  anticipations  were  not  long  in 
being  accomplished.  Eight  days  more  had  hardly  elapsed 
when  our  country  lost  one  of  its  most  virtuous  citizens  ; 
the  Academy  one  of  its  most  illustrious  members ;  and 
the  scientific  world,  a  genius  of  the  highest  order. 

Newton,  on  learning  the  premature  death  of  Cotes,  a 
young  geometer  whose  first  labours  had  led  to  great  ex- 
pectations, pronounced  those  words,  so  simple,  so  expres- 
sive, that  the  history  of  science  has  treasured  them  up  : 
« If  Cotes  had  lived  we  should  have  known  something  !  " 
From  the  mouth  of  Newton  this  short  eulogy  might  pass 
without  comment ;  it  belongs  to  genius  to  pronounce  such 
sentences,  and  we  shall  always  believe  its  word.  For 
myself,  Gentlemen,  devoid  of  all  such  authority  I  have 
felt  myself  bound  laboriously  to  go  through  so  many  de- 
tails, not  to  affirm,  but  to  prove  to  you,  that  we  know 
some  things  although  Fresnel  lived  so  short  a  time. 


THOMAS    YOUNG. 


A  Biography  read  at  a  Public  Sitting  of  the  Acad- 
emy OF  Sciences  the  26th  of  November,  1832. 


Gentlemen, — It  seems  as  if  death,  who  is  incessantly 
thinning  our  ranks,  directed  his  stroke  with  a  fatal  pre- 
dilection, against  that  class  of  our  body  so  limited  in  num- 
ber, our  foreign  associates.  In  a  short  space  of  time  the 
Academy  has  lost  from  the  list  of  its  members,  Herschel, 
whose  bold  ideas  on  the  structure  of  the  universe  have 
acquired  every  year  more  of  probability ;  Piazzi,  who  on 
the  first  day  of  the  present  century  presented  our  solar 
system  with  a  new  planet  ;  Watt,  who,  if  not  the  in- 
ventor of  the  steam-engine,  the  inventor  having  been  a 
Frenchman,*  was  at  least  the  creator  of  so  many  admi- 
rable contrivances,  by  the  aid  of  which  the  little  instru- 
ment of  Papin  has  become  the  most  ingenious,  the  most 
useful,  the  most  powerful  means  of  applying  industry; 

*  This  is  not  the  place  to  enter  on  the  controversy  respecting  the 
invention  of  the  steam-engine.  It  may,  however,  be  remarked,  that 
we  may  be  well  content  to  allow  it  to  remain  a  question  of  degree. 
Every  tea-kettle  is  a  steam-engine.  A  verj'  slight  and  obvious  con- 
trivance will  enable  steam  to  raise  a  piston.  Let  any  one  define  what 
tiiey  mean  precisely  by  the  term  steam-engine,  and  the  question  of 
prioritj"-  of  invention  will  be  easily  settled. —  Translator. 


INTRODUCTORY    REMARKS.  281 

Volta,  who  has  been  immortalized  by  his  electric  pile ; 
Davy,  equally  celebrated  for  the  decomposition  of  the 
alkalies  and  for  the  invaluable  safety  lamp  of  the  miner  ; 
Wollaston,  whom  the  English  called  the  pope,  because  he 
never  proved  follible  in  any  of  his  numerous  experiments, 
or  of  his  subtile  theoretical  speculations  ;  Jenner,  lastly, 
whose  discovery  I  have  no  need  to  extol  in  the  presence 
of  fathers  of  families.  To  pay  to  such  of  its  distin- 
guished oi-naments  the  legitimate  tribute  of  the  regret,  of 
the  admiration,  and  the  gratitude  of  all  men  devoted  to 
study,  is  one  of  the  principal  duties  which  the  Academy 
imposes  on  those  whom  it  invests  with  the  responsible 
honour  of  speaking  in  its  name  in  these  solemn  meetings. 
To  pay  this  grand  debt  with  the  least  possible  delay, 
seems  an  obligation  not  less  imperative.  Gentlemen,  the 
native  academician  always  leaves  behind  him,  among  the 
colleagues  with  whom  he  has  been  united  by  the  election 
of  the  Academy,  many  confidants  of  his  secret  thoughts, 
of  the  origin  and  course  of  his  researches,  of  the  vicissi- 
tudes which  he  has  gone  through.  The  foreign  associate 
on  the  contrary  resides  far  away  from  us  ;  he  rarely  joins 
in  our  meetings  ;  we  know  nothing  of  his  life,  his  habits, 
his  character,  unless  from  the  reports  of  travellers.  When 
several  years  have  passed  over  such  fugitive  documents, 
if  we  still  find  any  traces  of  them,  we  cannot  reckon  on 
their  accuracy.  Literary  intelligence  which  has  not  found 
a  recoi'd  in  print  is  a  sort  of  coin,  the  circulation  of  which 
alters  at -the  same  time  the  impression,  the  weight,  and 
the  inscription. 

These  reflections  tend  to  show  why  the  names  of  such 
men  as  Herschel,  Davy,  or  Volta  ought  to  be  mentioned 
in  our  assemblies  before  those  of  many  celebrated  acade- 
micians whom  death  has  snatched  fiom  our  more  imme- 


282  THOMAS    YOUNG. 

diate  circle.  Moreover,  I  hope  that  after  what  I  shall 
be  able  to  adduce,  even  in  a  few  minutes,  no  one  will  be 
able  to  deny  that  the  man  of  universal  science  whose  life 
I  am  about  to  describe,  and  whose  labours  I  shall  ana- 
lyze, has  some  real  claims  to  preference. 

BIRTH    OF    YOUNG. HIS    CHILDHOOD. PIUST    EN- 
TRANCE   ON    HIS    SCIENTIFIC    CAREER. 

Thomas  Young  was  born  at  Milverton  in  the  county 
of  Somerset,  June  13,  1773,  of  parents  who  belonged  to 
the  Society  of  Friends.  He  passed  his  earliest  years  at 
the  house  of  his  maternal  grandfather,  Mr.  Robert 
Davies,  of  Minehead,  whom  the  active  business  of  com- 
merce had  not  been  able  to  divert  from  the  cultivation  of 
classical  literature.  Young  could  read  fluently  at  the 
age  of  two  years.  His  memory  was  extraordinary.  In 
the  intervals  of  his  attendance  at  the  house  of  a  village 
schoolmistress  in  the  neighbourhood  of  Minehead,  at 
four  years  old,  he  had  learned  by  heart  a  number  of 
English  authors,  and  even  several  Latin  poems,  which 
he  could  repeat  from  beginning  to  end,  although  he  did 
not  understand  a  word  of  the  language.  The  example 
of  Young,  like  many  others  of  celebrity  recorded  by 
biographers,  may  then  contribute  to  keep  up  the  com- 
mon prepossession  of  so  many  good  fathers  of  families, 
who  see  in  certain  lessons  according  as  they  may  be 
recited  without  faults,  on  the  one  hand,  or  are  badly 
learnt  on  the  other,  infallible  indications  of  an  eternal 
mediocrity  in  the  one  case,  or  the  beginning  of  a  glorious 
career  in  the  other.  It  would  indeed  be  far  from  our 
object  if  these  historical  notices  should  tend  to  strengthen 
such  prejudices.  Thus,  without  wishing  to  weaken  the 
vivid  and  pure  emotions  which  every  year  the  distribu- 


HIS    EARLY    LIFK.  283 

tion  of  prizes  excites,  we  may  remind  some,  in  order  that 
they  may  not  abandon  themselves  to  dreams  which  they 
will  not  realize,  and  others,  in  order  to  fortify  thera 
against  discouragement,  that  Picus  de  Mirandola,  the 
phoenix  of  learners  of  all  ages  and  countries,  became  in 
mature  age  an  insignificant  writer  ;  that  Newton — that 
powerful  intellect  of  whom  Voltaire,  in  some  well  known 
lines,  asks  the  angels  whether  they  are  not  jealous, — the 
great  Newton,  we  observe,  made  but  indifferent  progress 
in  the  classes  of  his  school ;  that  study  had  for  him  no 
attractions  ;  that  the  first  time  he  felt  the  wish  to  labour 
it  was  merely  to  take  the  place  of  a  turbulent  school- 
fellow, who,  by  reason  of  his  rank  in  the  school  was 
seated  on  a  form  above  him  and  annoyed  him  by  kicks  ; 
that  at  the  age  of  twenty-two  he  was  a  candidate  for  a 
fellowship  at  Cambridge,  and  was  beaten  by  one  Robert 
Uvedale,  whose  name  but  for  this  circumstance,  would 
have  remained  to  this  day  perfectly  unknown ;  that 
Fontenelle,  lastly,  was  more  ingenious  than  exact  when 
he  applied  to  Newton  the  words  of  Lucan,  "  It  is  not 
given  to  men  to  see  the  Nile  feeble  and  at  its  source." 

At  the  age  of  six  years,  Young  entered  under  a  teacher 
at  Bristol,*  whose  mediocrity  was  a  fortunate  circum- 
stance for  him.  This,  Gentlemen,  is  no  paradox ;  the 
pupil,  not  being  able  to  accommodate  himself  to  the  slow 
and  limited  steps  which  his  master  took,  became  his  own 
instructor.  It  is  thus  that  those  brilliant  qualities  de- 
veloped themselves  which  too  much  aid  would  certainly 
have  enervated. 

*  The  master,  whose  name  was  King,  at  first  kept  school  at  Sta- 
pleton,  and  thence  removed  to  Townend,  both  near  Bristol.  Young's 
acquaintance  with  the  surveyor  commenced  after  he  quitted  that 
school.     See  Peacock's  Life,  p.  5. —  Translator. 


284  THOMAS    YOUNG. 

Young  was  only  eight  years  of  age,  when  chance, 
whose  influence  in  the  events  of  man's  life  is  more  con- 
siderable than  our  vanity  often  allows  us  to  admit,  took 
him  from  studies  exclusively  literary,  and  revealed  his 
real  vocation.  A  surveyor  of  much  merit  in  the  neigh- 
bourhood took  a  great  fancy  for  him  ;  he  took  him  out 
into  the  country  sometimes  on  holidays,  and  permitted 
him  to  amuse  himself  with  his  instruments  of  surveying 
and  natural  philosophy.  The  operations,  by  whose  aid 
the  young  scholar  saw  the  distances  and  elevations  of 
inaccessible  objects  determined,  powerfully  struck  his 
imagination.  But  soon  several  chapters  of  a  mathe- 
matical dictionary  made  all  that  seemed  mysterious  in 
the  matter  disappear.  From  this  moment,  in  his  Sun- 
day excursions,  the  quadrant  took  the  place  of  the  kite. 
In  the  evening,  by  way  of  amusement,  the  engineering 
novice  calculated  the  heights  measured  in  the  morning. 

From  the  age  of  nine  to  fourteen.  Young  went  to  a 
school  at  Compton  in  Dorsetshire,  kept  by  Mr.  Thom- 
son, whose  memory  he  always  cherished.  During  these 
five  years  all  the  pupils  of  the  school  were  occupied 
exclusively,  according  to  the  practice  of  English  Schools, 
in  a  minute  study  of  the  principal  writers  of  Greece  and 
Rome.*  Young  continually  maintained  his  place  at  the 
head  of  his  class :  and  yet  he  learned  at  the  same  time 
French,  Italian,  Hebrew,  Persian,  and  Arabic :  French 
and  Italian,  from  the  chance  object  of  satisfying  the 
curiosity  of  a   schoolfellow  who   possessed    some  works 

*  It  would  appenr  from  Young's  own  account,  that  a  far  more 
liberal  system  was  really  pursued  in  this  school.  Also,  the  praises 
of  the  usher,  Josiah  Jetlery,  should  never  be  omitted,  who  initiated 
Young  at  leisure  hours  into  a  variety  of  experimental  and  practical 
subjects,  which  contributed  materially  to  his  future  success.  See 
Peacock's  Life,  p.  6. —  Translator. 


SCIENTIFIC    STUDIES.  285 

printed  at  Paris,  of  wliicli  he  was  desirous  to  know  the 
contents : — Hebrew,  in  order  to  read  the  Old  Testament 
in  the  original :  Persian  and  Arabic,  with  the  view  of 
deciding  a  question  started  at  table,  whether  there  were 
as  marked  differences  between  the  Oriental  languages  as 
between  those  of  Europe  ? 

I  perceive  the  necessity  of  mentioning  that  I  write 
from  authentic  documents,  before  I  add  that  during  what 
might  appear  so  fabulous  a  progress  in  languages,  Young, 
during  his  walks  at  Compton,  was  seized  with  a  violent 
passion  for  botany  :  and  that  being  destitute  of  the  means 
of  magnifying  objects  of  which  naturalists  make  use  when 
they  wish  to  examine  the  delicate  parts  of  plants,  he  un- 
dertook to  construct  a  microscope  himself,  without  any 
other  guide  than  a  description  of  the  instrument  in  a 
work  by  Benjamin  Martin  :  that  to  arrive  at  this  difficult 
result  it  was  necessary  to  acquire  some  skill  in  the  art  of 
turning:  that  the  algebraic  formulas  of  the  optician 
having  presented  to  him  symbols  of  which  he  had  no 
idea  (those  of  Jiiixions),hG  was  for  a  moment  in  great 
perplexity  ;  but  not  being  willing  at  last  to  give  up  the 
enlargement  of  his  pistils  and  stamens,  he  found  it  more 
simple  to  learn  the  differential  calculus,  in  order  to  com- 
prehend the  unlucky  formula,  than  to  send  to  the  neigh- 
bouring town  to  buy  a  microscope.  The  ardent  activity 
of  the  juvenile  Young  had  led  him  to  exertions  beyond  the 
strength  of  his  constitution.  At  the  age  of  fourteen  his 
health  was  sadly  altered.  Various  indications  excited 
fears  of  a  disease  of  the  lungs  ;  but  these  menacing 
symptoms  at  length  yielded  to  the  prescriptions  of  art, 
and  the  anxious  cares  of  which  this  malady  made  him 
the  object  on  the  part  of  all  his  relations. 

It  is  rai'e  among  our  neighbours  on  the  other  side  of 


286  THOMAS    YOUNG. 

the  Channel  *  that  a  rich  person,  entrusting  his  son  to 
the  care  of  a  private  instructor,  does  not  seek  for  iiim  a 
fellow-pupil  of  the  same  age  among  those  who  have  been 
remarkable  for  their  success.  It  was  in  this  capacity  that 
Young  became,  in  1787,  the  fellow-pupil  of  the  grandson 
of  Mr.  David  Barclay,  of  Youngsbury,  in  Hertfordshire. 
On  the  day  of  his  first  appearance  there,  Mr.  Bai'clay, 
who  doubtless  felt  the  right  of  showing  himself  some- 
what exacting  with  a  scholar  of  fourteen  years  of  age, 
gave  him  several  phrases  to  copy,  with  the  view  of  as- 
certaining his  skill  in  penmanship.  Young,  perhaps 
somewhat  humiliated  by  this  kind  of  trial,  demanded,  in 
order  to  satisfy  him,  permission  to  retire  to  another 
room ;  this  absence  being  prolonged  beyond  the  time 
which  the  transcription  would  have  required,  Mr.  Bar- 
clay began  to  joke  on  the  want  of  dexterity  he  must 
evince,  when  at  length  he  reentered  tke  room.  The 
copy  was  remarkably  beautiful ;  no  writing-master  could 
have  executed  it  better :  as  to  the  delay,  there  was  no 
longer  any  need  to  speak  of  it,  for  "  the  little  qnaker,"  f 
as  Mr.  Barclay  called  him,  had  not  been  content  to  tran- 
scribe the  English  phrases  set  him  ;  he  had  also  trans- 
lated them  into  nine  different  languages. 

The  preceptor,  or  as  they  call  him  on  the  other  side  of 
the  Channel,  the  tutor,  who  had  to  direct  the  two  scholars 
at  Youngsbury  was  a  young  man  of  much  distinction,  at 
that  time  entirely  occupied  in  perfecting  himself  in  the 
knowledge  of  the  ancient  languages  ;  he  was  the  future 

*  The  reader  will  of  course  make  due  allowance  in  this  and  many 
other  passages  for  the  ideas  of  a  foreigner  as  to  English  habits.  The 
anecdote  of  Young's  penmanship  which  follows,  is  difterently  given 
by  Dr.  Peacock,  p.  12. —  Translator. 

t  This  seems  improbable,  as  Mr.  Barclay's  family  were  of  the  same 
sect. —  Translator. 


STUDIES    CHEMISTRY.  ^^\ 

author*  of  the  Calligraphia  Grgeca.  He  was  not  long, 
however,  in  perceiving  the  immense  superiority  of  one  of 
his  pupils,  and  he  recognized,  with  praiseworthy  modesty, 
that  in  their  common  studies  the  true  tutor  was  not 
always  he  who  bore  that  title.  At  this  period  Young 
drew  up,  continually  referring  to  the  original  sources,  a 
detailed  analysis  of  the  numerous  systems  of  philosophy 
which  were  professed  in  the  different  schools  of  Greece.f 
His  friends  spoke  of  this  work  with  the  most  lively  ad- 
miration. I  know  not  whether  the  public  is  destined 
ever  to  see  it.  At  all  events  it  was  not  without  influence 
on  the  life  of  its  author,  for  in  giving  himself  up  to  an 
attentive  and  minute  examination  of  the  singularities 
(to  use  a  mild  term)  with  which  the  conceptions  of  the 
Greek  philosophers  teemed,  Young  perceived  the  attach- 
ment which  he  retained  to  the  principles  of  the  sect  in 
which  he  was  born  became  weakened.  However,  he  did 
not  separate  entirely  from  it  till  some  years  afterwards, 
during  his  sojourn  in  Edinburgh. 

The  little  studious  colony  at  Youngsbury  quitted  the 
country  during  some  months  in  the  winter  to  reside  in 
London.  During  one  of  these  excursions  Young  met 
with  a  teacher  worthy  of  him.  He  was  initiated  into 
chemistry  by  Dr.  Higgins,  J  whose  name  I  can  the  less 
dispense  with  mentioning  since,  in  spite  of  his  earnest  and 
frequent  remonstrances,  there  was  an  obstinate  disincli- 
nation to  acknowledge  the  share  which  legitimately  be- 
longed   to  him   in    the   establishment  of  the  theory  of 

*  Mr.  Hodgkin. 

t  This  work  is  not  mentioned  by  Dr.  Peacock. —  Translator. 

J  The  share  borne  by  Dr.  Higgins  in  the  suggestion  or  discovery  of 
the  atomic  theory  has  been  variously  estimated.  For  an  apparently 
perfectly  fair  view  of  the  case,  the  reader  is  referred  to  Dr.  Daubeny's 
Atomic  Theory,  p.  33. —  Translator. 


288  THOMAS    YOUNG. 

definite  proportions,  one  of  the  most  valuable  discoveries 
of  modern  chemistry. 

Dr.  Brocklesby,  the  maternal  uncle  of  Young,  one  of 
the  most  popular  physicians  in  London  at  the  time,  justly 
confident  of  the  distinguished  success  of  the  young 
scholar,  communicated  occasionally  his  productions  to 
men  of  science  and  literature,  and  to  men  of  the  world, 
whose  approbation  might  have  greatly  flattered  his  van- 
ity. Young  thus  found  himself  at  an  early  period  in 
personal  relation  with  those  celebrated  men  Burke  and 
Wyndham,  of  the  House  of  Commons,  and  the  Duke  of 
Richmond.  The  last  nobleman,  then  Master  of  the 
Ordnance,  offered  him  the  place  of  private  secretary. 
The  two  other  statesmen,  although  they  wished  him  also 
to  follow  a  cai'eer  connected  with  the  public  administra- 
tion, yet  advised  him  first  to  go  through  a  course  of  law 
at  Cambridge.*  With  such  powerful  patrons  Young 
might  reckon  on  one  of  those  lucrative  oflSces  which 
persons  in  power  are  not  slow  to  bestow  on  those  who 
will  spare  them  all  study  and  application,  and  daily 
furnish  them  with  the  means  of  shining  at  the  court, 
the  council,  the  senate,  without  compromising  their  van- 
ity by  committing  any  indiscretion.  Young  happily  had 
a  consciousness  of  his  powers  ;  he  perceived  in  himself  ■ 
the  germ  of  those  brilliant  discoveries  which  have  since 
adorned  his  name :  he  preferred  the  laborious,  but  inde- 
pendent, career  of  the  man  of  letters,  to  the  golden 
chains  which  they  exhibited  so  temptingly  to  hi§  eyes. 
Honour  be  to  him  for  such  a  determination !  May  his 
example  serve  as  a  lesson  to  so  many  young  men  whom 

*  "  Mr.  Wyndham  advised  him  not  to  accept  the  appointment,  and 
recommended  him  rather  to  proceed  to  Cambridge,  and  study  the  law." 
Peacock's  Life,  p.  45. —  Translator. 


STUDIES    MEDICINE.  289 

political  ambition  diverts  from  a  more  noble  vocation,  to 
transform  themselves  into  mere  officials  ;  but  who  might 
learn,  like  Young,  to  turn  their  eyes  to  the  future,  and 
not  sacrifice  to  the  futile  and  transitory  satisfaction  of 
being  surrounded  by  persons  soliciting  favours,  tlie  solid 
testimonies  of  esteem  and  gratitude  which  the  public 
rarely  fails  to  otfer  to  intellectual  labours  of  a  high 
order ;  and  if  it  happen  in  the  illusions  of  inexperience, 
that  they  should  think  too  heavy  a  sacrifice  imposed  on 
them,  we  would  ask  them  to  take  a  lesson  of  ambition 
from  the  mouth  of  a  great  captain  whose  ambition  knew 
no  bounds  ;  to  meditate  on  the  words  which  the  First 
Consul,  the  victor  of  Marengo,  addressed  to  one  of  our 
most  honoured  colleagues  (M.  Lemercier)  on  the  day 
when  he,  quite  in  accoi'dance  with  his  character,  had  just 
refused  a  place  then  of  great  importance,  that  of  Coun- 
cillor of  State  : — 

"  I  understand,  Sir,  you  love  literature,  and  you  wish  to 
belong  altogether  to  it.  I  have  nothing  to  oppose  to  this 
resolution.  Yes !  I,  myself,  if  I  had  not  become  a 
General-in-chief,  and  the  instrument  of  the  fate  of  a 
great  nation,  do  you  think  I  would  have  gone  through 
the  offices  and  the  salons,  to  put  myself  in  dependence 
on  whoever  might  happen  to  be  in  power  in  the  position 
of  minister  or  ambassador  ?  No  !  no !  I  would  have 
taken  to  the  exact  sciences.  I  would  have  made  my 
way  in  the  path  of  Galileo  and  Newton  :  and,  since  I 
have  succeeded  constantly  in  my  great  enterprises,  truly 
I  should  have  been  equally  distinguished  by  my  scientific 
labours.  I  should  have  left  behind  me  the  remembrance 
of  great  discoveries.  No  other  kind  of  glory  would  have 
tempted  my  ambition." 

Young  made  choice  of  the  profession  of  medicine,  in 

fcEC.    SF.R.  13 


290  THOMAS    YOUNG. 

which  he  hoped  to  find  fortune  and  independence.  His 
naedical  studies  were  commenced  in  London  under  Baillie 
and  Cruikshank  ;  he  continued  them  at  Edinburgh,  where 
at  that  time  Drs.  Black,  Munro,  and  Gi-egory  were  in  the 
height  of  tlieir  celebrity.  It  was  only  at  Gottingen,  in 
the  following  year  (17'J5),  that  he  took  the  degree  of 
Doctor.*  Before  going  through  this  form,  so  empty,  yet 
always  so  imperatively  exacted.  Young,  hardly  beyond 
the  period  of  youth,  had  become  known  to  the  scientific 
world  by  a  note  relative  to  the  gum  ladanum  ;  by  the 
controversy  which  he  sustained  against  Dr.  Beddoes  on 
the  subject  of  Crawford's  theory  of  heat ;  by  a  memoir 
on  the  habits  of  spiders,  and  the  theory  of  Fabricius, 
the  whole  enriched  with  erudite  researches  ;  and  lastly, 
by  an  inquiry  on  which  I  will  enlarge  on  account  of  its 
great  merit,  the  unusual  favour  with  which  it  was  re- 
ceived at  its  first  production,  and  the  neglect  into  which 
it  has  since  fallen. 

The  Royal  Society  of  London  enjoys  throughout  the 
whole  kingdom  a  vast  and  deserved  consideration.  The 
Philosophical  Transactions  which  it  publishes  have  been 
for  more  than  a  century  and  a  half  the  glorious  archives 
in  which  British  genius  holds  it  an  honour  to  deposit  its 
titles  to  the  recognition  of  posterity.  The  wish  to  see 
his  name  inscribed  in  the  list  of  fellow-labourers  in  this 
truly  national  collection,  beside  the  names  of  Newton, 
Bradley,    Priestley,    and    Cavendish    has    always    been 

*  The  author  has  omitted  that,  in  1797,  Young  entered  as  a  fellow- 
commoner  at  Emmanuel  College,  Cambridge ;  and  in  due  time  gradu- 
ated there  regularly  in  medicine;  a  step  at  that  time  necessary  for  his 
admission  to  the  College  of  Physicians,  in  order  to  enable  him  to 
practise  as  a  physician  in  London.  See  Peacock's  Life,  p.  115.  In 
the  university  he  was  familiarly  known  by  the  name  of"  Phenomenon 
Young." —  Translator. 


PAPER    ON    VISION.  291 

among  the  students  of  the  celebrated  universities  of 
Cambridge,  Oxford,  Edinburgh,  and  Dublin,*  the  most 
anxious  as  well  as  legitimate  object  of  emulation.  Here 
is  always  the  highest  point  of  ambition  of  the  man  of 
science  ;  he  does  not  aspire  to  it  unless  on  occasion  of 
some  capital  investigation ;  and  the  first  attempts  of  his 
youth  come  before  the  public  by  a  channel  better  suited 
to  their  importance,  by  the  aid  of  one  of  those  numerous 
periodicals  which,  among  our  neighbours,  have  contri- 
buted so  much  to  the  progress  of  human  knowled"-e. 
Such  is  the  ordinary  coui'se  ;  such  consequently  ought 
not  to  have  been  the  course  followed  by  Young ;  at  the 
age  of  twenty  he  addressed  a  paper  to  the  Royal  Society. 
The  council,  composed  of  the  most  eminent  men  of  the 
Society,  honoured  this  paper  with  their  suffrage,  and  it 
soon  after  appeared  in  the  Philosophical  Transactions. 
The  author  treated  in  it  of  the  subject  of  vision. 


THEORY    OF    VISION. 

The  problem  was  any  thing  but  new.  Plato  and  his 
disciples,  four  cehtuiies  before  our  era,  were  occupied 
with  it ;  but  at  the  present  day  their  conceptions  can 
hardly  be  cited  but  to  justify  the  celebrated  and  little 
flattering  sentence  of  Cicero :  "  There  is  nothing  so 
absurd  that  it  has  not  been  said  by  some  of  the  phi- 
losophers." 

After  passing  over  an  interval  of  2000  years,  we  must 
from  Greece  transport  ourselves  to  Italy,  if  we  would  find 
any  ideas  on  the  wonderful  subject  of  vision  which  merit 
the  remembrance  of  the  historian.     Where,  without  hav- 

*  And,  it  might  be  added,  probably  to  a  far  more  numerous  class 
not  of  those  bodies. —  Translator. 


292  THOMAS    YOUNG. 

ing  ever,  like  the  philosopher  of  Egina,  proudly  closed 
their  school  against  all  wlio  were  not  geometers,  careful 
experimenters  marked  out  the  sole  route  by  which  it  is 
permitted  to  man  to  arrive  without  false  steps  at  the  con- 
quest of  unknown  regions  of  truth  ;   there  Maurolycus 
and  Porta  proclaimed  to  their  contemporaries  that  the 
problem  of  discovering  what  is  presents  sufficient  diffi- 
culties to  render  it  at  least  somewhat  presumptuous  to 
cast  ourselves  upon  the  world  of  intelligences  to  search 
after  what  ought  to  he  ;  there  these  two  celebrated  fellow 
countrymen  of  Archimedes  commenced  the  explanation 
of  the  functions  of  the  different  media  of  which  the  eye 
is  composed  ;  and  showed  themselves  contented,  as  were 
at  a  later  period   Galileo  and    Newton,  not  to  ascend 
above  those  kinds  of  knowledge  which  are  capable  of 
being  elaborated  or  corrected  by  the  aid  of  our  senses, 
and  which  had  been  stigmatized  under  the  porticos  of 
the   Academy  by   the    contemptuous    epithet   of   simple 
opinion.     Such  is  always   human   weakness  that,  after 
having  followed  with  a  rare  success  the  principal  devia- 
tions which  light  undergoes  in  passing  through  the  cornea 
and  the  crystalline,  Maurolycus  and  Porta,  when  very 
near  attaining  their  object,  stopped  short,  as  if  before  an 
insurmountable  difficulty,  when  it  was  objected  to  their 
theory  that  objects  ought  to  appear  in  an  inverted  posi- 
tion if  the  images  formed  in   the  eye  are  themselves 
inverted.     The   adventurous   spirit   of   Kepler,   on    the 
contrary,    did    not    remain    embarrassed.     It    was    from 
psychology  that  the   attack  originated  ;  it  was   equally 
from  psychology — clear,  precise,  and  mathematical — that 
he  overthrew  the  objection.     Under  the  powerful  hand 
of   this   great   man,    the    eye   became,  definitively,  the 
simple   optical    apparatus   known    by   the   name  of  the 


THEORY    OF    THE    EYE.  293 

camera  obscura  ;  the  retina  is  the  ground  of  the  picture, 
the  crystalline  replaces  the  glass  lens.* 

This  assimilation,  generally  adopted  since  Kepler's 
time,  remains  open  only  to  one  diificulty  ;  the  camera 
obscura,  like  an  ordinary  telescope,  requires  to  be  brought 
to  a  projjer  focus  according  to  the  distance  of  objects. 
When  objects  are  near  it  is  indispensable  to  increase  the 
distance  of  the  picture  from  the  lens  ;  a  contrary  move- 
ment becomes  necessary  as  they  become  more  distant. 
To  preserve  to  the  images  all  the  distinctness  which  is 
desirable,  without  changing  the  position  of  the  surface 
which  receives  them,  is  therefore  impossible  :  at  least, 
always  supposing  the  curvature  of  the  lens  to  remain 
invariable ;  that  it  cannot  increase  when  we  look  at  near 
objects,  or  diminish  for  distant  objects. 

*  The  author  seems  to  have  left  this  illustration  incomplete.  Kep- 
ler's suggestion  of  the  identity  of  the  eye  with  the  camera  obscura, 
after  all,  does  not  touch  the  difficulty  of  the  inversion  of  the  image. 
Nor  has  it  been  considered  as  completely  cleared  up  even  till  much 
later  times.  The  solution  which,  it  is  believed,  is  now  most  generally 
assented  to  is  this.  It  is  a  law  of  our  constitution,  dependent  on  some 
physiological  principle  unknown,  that  we  refer  impressions  on  the 
retina  to  objects  existing,  or  believed  to  exist,  in  the  rectilinear  direc- 
tion fi-om  which  the  impression  comes  to  tlie  retina.  Consequently, 
as  rays  cross  at  the  pupil,  an  impression  arriving  at  (r)  in  the  direction 


of  the  arrow,  will  convey  the  idea  of  an  object  existing  at  (5') ;  in  other 
words,  a  ray  falling  on  the  upper  part  of  the  retina  suggests  an  object 
Ij'ing  bekiw,  or  an  inverted  image  suggests  an  ei^ect  object. 


294  THOMAS    YOUNU. 

Among  the  different  modes  of  obtaining  distinct  images, 
nature  has  assuredly  made  a  choice,  since  man  can  see 
with  great  distinctness  at  very  different  distances.  The 
question  thus  put  has  afforded  a  wide  subject  of  remark 
and  discussion  to  physicists,  and  great  names  have  figured 
in  the  debate. 

Kepler  and  Descartes  held  that  the  whole  ball  of  the 
eye  is  susceptible  of  being  elongated  and  flattened. 

Porterfield  and  Zinn  contended  that  the  crystalline 
lens  was  movable  ;  and  that  it  could  place  itself  nearer 
to,  or  further  from  the  retina,  as  might  be  needed. 

Jurin  and  Musschenbroeck  believed  in  a  change  in  the 
curvature  of  the  cornea. 

Sauvages  and  Bourdelot  supposed  also  that  a  change 
in  curvature  took  place,  but  only  in  the  crystalline  lens. 
Such  is  also  the  system  of  Young.  Two  memoirs  which 
our  colleague  successively  submitted  to  the  Royal  Society 
of  London  include  the  complete  development  of  his  views. 

In  the  first  of  these,  the  question  is  treated  almost 
entirely  in  an  anatomical  point  of  view.  Young  there 
demonstrates  by  the  aid  of  direct  observations  of  a  very 
delicate  kind,  that  the  crystalline  is  endowed  with  a 
fibrous  or  muscular  constitution,  admirably  adapted  to 
all  sorts  of  changes  of  form.  This  discovery  overthrew 
the  only  solid  objection  which  had,  till  then,  opposed  the 
hypothesis  of  Sauvages  and  Bourdelot. 

That  hypothesis  had  no  sooner  been  announced  than  it 
had  been  attacked  by  Hunter. 

Thus  this  celebrated  anatomist  aided  the  cause  of  the 
young  experimenter  by  the  attention  drawn  to  the  sub- 
ject, while  his  labours  were  as  yet  unpublislied,  and  not 
even  communicated  to  any  one.  Howevei",  this  point  of 
the   discussion   soon   lost   its   importance.      The   learned 


THKORY    OF    THE    EYE.  295 

Leuwenlioeck,  armed  with  his  powerful  microscopes, 
traced  out,  and  gave  figures  of,  the  muscular  fibres  in 
all  their  ramitications  ia  the  crystalline  of  a  fish.  To 
awaken  the  attention  of  the  scientific  world,  tired  with 
these  long  debates,  nothing  less  was  necessary  than  the 
high  renown  of  two  new  members  of  the  Royal  Society 
who  entered  the  lists  :  one,  a  celebrated  anatomist,  the 
other  the  most  eminent  instrument-maker  of  whom  Eng- 
land could  boast.  These  jointly  presented  to  the  Royal 
Society  a  memoir,  the  fruit  of  their  combined  labours, 
intended  to  establish  the  complete  unalterability  of  the 
form  of  the  crystalline.  The  scientific  world  was  not 
prepared  to  admit  that  Sir  Everard  Home  and  Ramsden 
together,  could  possibly  make  inaccurate  experiments,  or 
be  deceived  in  micrometical  measurements.  Young  him- 
self could  not  believe  it  ;  and  in  consequence  he  did  not 
hesitate  publicly  to  renounce  his  theory. 

This  readiness  to  own  himself  vanquished,  so  rare  in 
a  young  man  of  twenty-five,  and  especially  on  the  occa- 
sion of  a  first  publication,  was  in  this  instance  an  act  of 
modesty  without  example.  Young,  however,  had  really 
nothing  to  retract.  In  1800,  after  having  withdraAvn 
his  former  disavowal,  our  colleague  developed  anew  the 
theory  of  the  change  of  form  of  the  crystalline  in  a  me- 
moir against  which,  from  that  time,  no  serious  objection 
has  been  brought. 

Nothing  could  be  more  simple  than  his  line  of  aro-u- 
ment  ;  nothing  more  ingenious  than  his  experiments. 
Young,  in  the  first  instance,  got  rid  of  the  hypothesis 
of  a  change  of  curvature  in  the  cornea  by  the  aid  of 
microscopic  observations,  which  were  of  a  kind  to  ren- 
der the  most  minute  variations  appreciable.  We  can 
say  more  ;  he  placed  the  eye  in  special  conditions  where 
changes    of  curvature   in   the   cornea  would  have    been 


296  THOMAS    YOUNG. 

■without  eifect ;  he  phinged  the  eye  in  water,  and  proved 
that  there  was  still  the  same  faculty  of  seeing  at  different 
distances  perfectly  preserved.  Tlie  second  of  three  pos- 
sible suppositions,  that  of  an  alteration  in  the  dimensions 
of  the  whole  organ,  was  again  overthrown  by  a  multitude 
of  objections  and  of  experiments  which  it  was  difficult  to 
resist. 

The  problem  thus  seemed  finally  settled.  Who  does 
not  see,  in  fact,  that  if,  of  three  only  possible  solutions, 
two  are  put  out  of  the  question,  the  third  is  necessarily 
established  ;  that  if  the  radius  of  curvature  of  the  cornea 
and  the  longitudinal  diameter  of  the  wJwIe  eye  are  inva- 
riable, it  must  follow  that  the  form  of  the  crystalline  is 
invariable  ?  Young,  however,  did  not  stop  there  ;  he 
proved  directly,  by  the  minute  phenomena  of  the  changes 
in  the  images,  that  the  crystalline  really  changes  its  cui'- 
vature ;  he  invented,  or  at  least,  gave  perfection  to,  an 
instrument  susceptible  of  being  employed  even  by  the 
least  intelligent  persons,  and  those  least  accustomed  to 
delicate  experiments  ;  and,  armed  with  this  new  means 
of  investigation,  he  assured  himself  that  those  individuals 
in  whose  eyes  the  crystalline  has  been  removed  in  the 
operation  for  cataract,  did  not  enjoy  the  faculty  of  seeing 
equally  distinctly  at  all  distances.* 

*  This  instrument,  called  an  "  Optometer,"  was  originally  proposed 
by  Dr.  Porterfield,  and  consists  of  a  simple  and  ingenious  contrivance 
for  ascertaining  the  focal  length  of  the  eye,  which  varies  so  greatly  in 
different  individuals,  and  often  in  two  eyes  of  the  same  person,  and  in 
the  same  eye  under  different  conditions.  Dr.  Young  greatly  improved 
upon  the  original  construction.  It  will  be  found  described  in  the  Lec- 
tures on  Natural  Philosopluj,  vol.  ii.  p.  576.  The  principle  of  it  consists 
in  measuring  accurately  the  distance  of  an  object  from  the  eye  at 
which  perfectly  distinct  vision  is  obtained,  and  which  is  determined 
when  the  object,  seen  through  two  small  apertures  close  to  the  eye, 
presents  only  a  single  image,  while  in  other  positions  it  shows  two 
images. —  Translator. 


VISION    AT    DIFFERENT    DISTANCES.  297 

We  might  fairly  be  astonished  that  this  admirable  the- 
ory of  vision,  this  combination  so  well  framed  when  the 
most  ingenious  reasonings  and  experiments  lent  each 
other  mutual  support,  did  not  occupy  that  distinguished 
rank  in  the  science  of  the  country  which  it  deserved. 
But  to  explain  this  anomaly,  must  we  necessarily  recur 
to  a  sort  of  fatality  ?  Was  Young  then  really,  as  he 
sometimes  described  himself  with  vexation,  a  new  Cas- 
sandra, proclaiming  incessantly  important  truths  which 
his  ungrateful  contemporaries  refused  to  receive  ?  We 
should  be  less  poetical,  but  more  true,  it  seems  to  me,  if 
we  remarked  that  the  discoveries  of  Young  were  not 
known  to  the  majority  of  those  who  would  have  been 
able  to  appreciate  them.  The  physiologists  did  not  read 
his  able  memoir,  because  in  it  he  presumes  upon  more 
mathematical  knowledge  than  is  usually  attained  in  that 
branch. 

The  physicists  neglected  it  in  their  turn,  because  in 
oral  lectures,  or  printed  works,  the  public  demands  little 
more  at  the  present  day  than  superficial  notions,  which 
an  ordinary  mind  can  penetrate  without  difficulty.  In  all 
this,  whatever  our  distinguished  colleague  may  have  be- 
lieved, we  perceive  nothing  out  of  the  ordinary  course. 
Like  all  those  who  sound  the  greatest  depths  of  science, 
he  was  misunderstood  by  the  multitude ;  but  the  applauses 
of  some  of  the  select  few  ought  to  have  recompensed  him. 
In  such  a  question  we  ought  not  to  count  the  suffrages ; — 
it  is  more  wise  to  tveigh  them.* 

*  Arago,  in  assigning  tlie  probable  causes  of  the  neglect  of  Young's 
speculations,  seems  to  fall  short  of  his  usual  point  and  perspicuity.  It 
might  be  true  that  his  memoir  was  neglected  by  physiologists  because 
it  was  mathematical,  and  by  parity  of  reason  it  might  have  been  neg- 
lected by  physicists  and  mathematicians  as  being  physiological.  But 
it  is  surely  no  reason  to  say  that  it  was  neglected  by  physicists  because 
l.S  * 


298  THOMAS    YOUNG. 


INTERFERENCES. 

The  most  beautiful  discovery  of  Young,  that  which  will 
render  his  name  imperishable,  was  suggested  to  him  by 
an  object  in  appearance  very  trivial ;  by  those  soap  bub- 

the  public  are  superficial,  &c.  Young  may  have  been,  in  most  of  his 
speculations,  too  profound  for  the  many;  but  this  particular  instance 
of  the  structure  of  the  eye  and  theory  of  vision  is,  perhaps,  of  all  his 
researches,  that  which  can  be  the  least  open  to  this  charge.  The  sub- 
ject is  not  itself  abstruse:  it  is  one  easily  understood  bj'  every  edu- 
cated person,  without  mathematical  attainments ;  and  the  point  at 
issue  was  a  simple  question  of  fact  requiring  no  profound  physiological 
knowledge  to  appreciate,  whether  the  crystalline  has  or  has  not  a  mus- 
cular structure  capable  of  changing  its  convexity.  The  real  state  of 
the  case  seems  to  be  very  satisfactorially  explained  by  Dean  Peacock 
(p.  36,  et  seq.),  from  whose  account,  as  well  as  from  what  has  been  since 
written,  it  appears,  after  all  that  has  been  done  both  by  Dr.  Young  and 
others,  that  there  is  even  at  the  present  day  considerable  difference  of 
opinion  on  the  subject. 

Perhaps  the  most  comprehensive  survey  of  the  whole  subject  which 
recent  investigation  has  produced  will  be  found  in  the  paper  of  Pro- 
fessor J.  D.  Forbes  in  the  jE/lin.  Traiisat turns,  vol.  xvi.  part  I.  1845. 
After  giving  a  summarj'  view  of  preceding  researches,  and  adverting 
to  the  prevalent  opinion  atnong  men  of  science,  that  the  true  explana- 
tion yet  remains  to  be  discovered  (most  anatomists  den3'ing  as  a  fact 
the  existence  of  the  muscular  structure  which  Young  conceived  he  had 
proved).  Professor  Forbes  proposes,  as  his  own  view  of  the  cause,  the 
consideration  of  the  remarkable  varialiuii  in  density  of  the  crystalline 
towards  its  central  part;  coats  of  different  density  being  disposed  in 
different  layers,  may  be  acted  ou  by  the  pressure  of  the  humours  of 
the  eye  when  the  external  action  of  the  muscles  compresses  them,  and 
thus  increase  tlie  curvature  of  the  lens,  when  the  eye  is  directed  to  a 
near  object,  the  whole  consistence  especially  in  the  outer  parts  being 
of  a  gelatinous  or  compressible  nature,  and  the  central  part  more  solid 
and  more  convex.  Thus  uniform  pressure  on  the  outer  parts  would 
tend  to  make  the  outer  parts  conform  more  nearly  to  the  more  convex 
interior  nucleus. 

It  may  be  added  that  mtiiiy  physiologists  are  of  opinion  that,  after  all, 
there  does  not  exist  a  sufficient  compressive  action  on  the  ball  of  the 
eye  to  produce  the  effect  supposed. —  Trandatur. 


INTERFERENCES.  299 

bles  so  brilliantly  coloured,  so  light,  wliicli  when  just 
blown  out  of  a  pipe  become  the  sport  of  every  impercep- 
tible current  of  air.  Before  so  enlightened  an  audience, 
it  would  without  doubt  be  superfluous  to  remark  that  the 
difficulty  of  producing  a  phenomenon,  its  variety,  its  util- 
ity to  the  arts,  are  not  the  necessary  indications  of  its 
importance  in  a  scientific  point  of  view.  I  have,  there- 
fore, to  connect  with  a  child's  sport  the  discovery  which 
I  proceed  to  analyze,  with  the  certainty  that  its  credit 
will  not  suffer  from  its  origin.  At  any  rate  I  shall  have 
no  need  to  recall  the  apple,  which,  dropping  from  its  stalk 
and  falling  unexpectedly  at  the  feet  of  Newton,  developed 
the  ideas  of  that  great  man  respecting  the  simple  and 
comprehensive  laws  which  regulate  the  celestial  motions  ; 
nor  the  frog  and  the  touch  of  the  bistoury,  to  which  phys- 
ical science  has  recently  been  indebted  for  the  marvellous 
pile  of  Volta.  Without  referring  in  particular  to  soap 
bubbles,  I  will  suppose  that  a  physicist  has  taken  for  the 
subject  of  experiment  some  distilled  water,  that  is  to  say, 
a  liquid,  which  in  its  state  of  pui'ity  never  shows  any 
more  than  some  very  slight  shade  of  colour,  blue  or  green, 
hardly  sensible,  and  thaj;  only  when  the  light  traverses 
great  thicknesses.  I  would  next  ask  what  we  should 
think  of  his  veracity  if  he  were  to  announce  to  us,  with- 
out further  explanation,  that  to  this  water,  so  limpid,  he 
could  at  pleasure  communicate  the  most  resplendent  col- 
ours ;  that  he  knew  how  to  make  it  violet,  blue,  green  ; 
then  yellow  like  the  peel  of  citron,  or  red  of  a  scarlet  tint, 
without  affecting  its  purity,  without  mixing  with  it  any 
foreign  substance,  Avithout  changing  the  proportions  of  its 
constituq^it  gaseous  elements.  Would  not  the  public  re- 
gard our  physicist  as  unworthy  of  all  belief,  especially 
when,  after  such  strange  assertions,  he  should  add,  that 


300  THOMAS    YOUNG. 

to  produce  colour  in  water,  it  suffices  to  reduce  it  to  the 
state  of  a  thin  fihu  ;  tliat  ''thin"  is,  so  to  speak,  the  syn- 
onym of  "coloured  ; "  that  the  passage  of  each  tint  into 
one  the  most  different  from  it  is  the  necessary  conse- 
quence of  a  simple  variation  of  the  thickness  of  the  liquid 
film  ;  that  this  variation,  for  instance,  in  passing  from  red 
to  green,  is  not  the  thousandth  part  of  the  thickness  of  a 
hair  !  Yet  these  incredible  propositions  are  only  the 
necessary  consequences  deduced  from  the  accidental  ob- 
servation of  the  colours  presented  by  soap  bubbles,  and 
even  by  extremely  thin  films  of  all  sorts  of  substances. 

To  comprehend  how  such  phenomena  have,  during 
more  than  2000  years,  daily  met  the  eyes  of  philoso- 
phers without  exciting  their  attention,  we  have  need  to 
recollect  to  how  few  persons  nature  imparts  the  valuable 
faculty  of  being  astonished  to  any  purpose. 

Boyle  was  the  first  to  penetrate  into  this  rich  mine. 
He  confined  himself,  however,  to  the  minute  description 
of  the  varied  circumstances  which  gave  rise  to  these 
iridescent  colours.  Hooke,  his  fellow-labourer,  went  fur- 
ther. He  believed  that  he  had  discovered  the  cause  of 
this  kind  of  colours  in  the  coincidences  of  the  rays,  or  to 
speak  in  his  own  language,  in  the  mutual  action  on  each 
other  of  the  waves  reflected  by  the  two  surfaces  of  the 
thin  film.  This  was,  we  may  admit,  a  suggestion  char- 
acteristic of  genius  ;  but  it  could  not  be  made  use  of  at 
an  epoch  when  the  compound  nature  of  white  light  was 
not  as  yet  understood. 

Newton  made  the  colours  of  thin  films  a  favourite 
object  of  study.  He  devoted  to  them  an  entire  book  of 
his  celebrated  treatise  the  "  Optics."  He  established 
the  laws  of  their  formation  by  an  admirably  connected 
chain  of  experiments,  whi(;h  no  one  has  since  surpassed 


COLOURS    OF    THIN    FILMS.  301 

in  excellence.  In  illuminating  with  homogeneous  light 
the  very  regularly  formed  series  of  bands  of  which 
Hooke  had  already  made  mention,  and  which  originated 
round  the  point  of  contact  of  two  lenses  pressed  closely 
together,  he  proved  that  for  each  species  of  simple 
colour  there  exists,  in  thin  films  of  every  substance,  a 
series  of  thicknesses  gradually  increasing,  at  each  of 
which  no  light  is  reflected  from  the  film.  This  result 
was  of  capital  importance ;  it  included  the  key  to  all 
these  phenomena. 

Newton  was  less  happy  in  the  theoretical  views  which 
these  remarkable  observations  suggested  to  him.  To 
say,  with  him,  that  the  luminous  ray  which  is  reflected 
is  "in  a  fit  of  easy  reflexion," — to  say  that  the  ray 
which  passes  through  the  film  entire,  is  "  in  a  fit  of  easy 
transmission," — what  is  it  but  to  announce,  in  obscure 
terms,  merely  the  same  fact  which  the  experiment  with 
the  two  lenses  has  already  taught  us  ?  * 

*  In  regard  to  the  theory  of  the  "  fits,"  the  author  here  seems  to 
represent  Newton's  view,  as  in  fact  mere  tautology;  while  in  other 
places  he  is  supposed  to  have  indulged  in  a  visionary  theory  on  the 
subject.  Newton,  however,  expressly  says,  "  what  kind  of  action  or 
disposition  this  is ; — whether  it  consist  in  a  circulating  or  vibrating 
motion  of  the  ray,  or  of  the  medium,  or  something  else,  I  do  not  here 
inquire."     (Optics,  p.  255,  ed.  1721.) 

The  fact  is,  Newton  in  his  optical  researches  expressed  the  same 
avowed  and  systematic  dislike  to  indulging  in  a7iy  gratuitous  theories 
as  in  his  other  inquiries.  "  Hypotheses  non  fingo  "  was  his  motto  in 
these  as  well  as  other  researches.  In  adopting  the  idea  of  "  fits  of 
easy  reflexion  and  transmission,"  we  are  of  opinion  that  he  did  not 
violate  that  maxim,  and  that  it  was  in  fact  the  only  legitimate  first 
expression  of  the  conclusion  which  the  facts  warranted.  At  certain 
points  no  light  appeared;  it  was  the  legitimate  inference,  in  the  then 
state  of  knowledge,  that  none  was  reflected.  But  light  was  clearly 
under  the  same  circumstances  transmitted ;  at  a  distance  a  little 
greater  along  the  ray,  an  opposite  effect  was  witnessed;  and  so  on. 


302  THOMAS     YOUNG. 

The  theory  of  Thomas  Young  is  not  amenable  to  this 
criticism.  Here  there  is  no  longer  admitted  any  peculiar 
kind  of  "  fits "  as  primordial  properties  of  the  rays. 
The  thin  film  is  here  assimilated  in  all  respects  to  any 
thicker  reflector  of  the  same  substance.  If  at  certain 
points  in  its  surface  no  light  is  visible,  Young  did  not 
conclude  that  therefore  its  reflexion  had  ceased  ;  he  sup- 
posed tliat,  in  the  special  directions  of  those  points,  the 
rays  reflected  by  the  second  surface  proceeded  to  meet 
with  those  reflected  from  the  first  surface,  and  com- 
pletely destroyed  them.  This  conflict  of  the  rays  is 
what  the  author  designated  by  the  term  "  interference^ 
which  has  since  become  so  famous. 

Observe  then  here  the  most  singular  of  hypotlieses  ! 
We  must  certainly  feel  surprised  at  finding  night  in  full 
sunshine,  at  points  where  the  rays  of  that  luminary 
ari'ive  freely  ;  but  who  would  have  imagined  that  we 
should  thence  come  to  suppose  that  darkness  could  be 
engendered  by  adding  light  to  light ! 

A  physicist  is  truly  eminent  when  he  is  able  to  an- 
nounce any  result  which,  to  such  an  extent,  clashes  with 
all  received  ideas  ;  but  he  ought,  without  delay,  to  sup- 
port his  views  by  demonstrative  proofs,  under  the  pen- 
alty of  being  assimilated  to  those  Oriental  writers  whose 
fantastic  reveries  charmed  the  thousand  and  one  nights 
of  the  Sultan  Schahriar. 

It  was  nothing  more  than  the  strict  inference  that  at  those  points  suc- 
cessively something  occurred  in  the  course  of  the  ray  which  disposed  it 
for,  or  induced,  reflexion  in  tlie  one  case,  and  non-reflexion  in  the 
other;  accompanied  in  the  latter  case  by  the  like  tendency  to  trans- 
misi^ion.  These  apparent  "fits"  must  be  still  acknowledged  as />/ie- 
nomena;  the  mechanism  by  which  they  are  produced  is,  however,  now 
known  to  be  nothing  inherent  in  the  light,  no  essential  property  re- 
curring, but  the  simple  periodicity  of  conspiring  or  counteracting 
wave-action. —  Translator. 


INTERFERENCE    OF    LIGHT.  303 

Young  had  not  this  degree  of  prudence.  He  showed 
at  once  that  his  theory  would  agree  with  the  phenomena, 
but  without  going  beyond  mere  possibiHty.  When  at  a 
later  period  he  arrived  at  real  proofs  of  it,  the  public 
had  other  prepossessions,  which  he  was  not  able  to  over- 
come. However,  the  experiment,  whence  our  colleague 
deduced  so  memorable  a  discovery,  could  not  excite  the 
shadow  of  a  doubt.* 

*  In  the  retrospective  glance  which  the  author  thus  gives  over  the 
progress  of  discovery  previous  to  the  period  at  which  Dr.  Young  first 
entered  on  the  field,  what  we  have  chiefly  to  observe  is,  that  up  to 
that  date  nothing  like  a  connected  view  of  the  physical  character  of 
this  wonderful  agent  had  been  attained ;  a  few  isolated  speculations 
had  indeed  been  put  forth  respecting  a  theory  of  emitted  molecules 
on  the  one  hand,  and  of  waves  in  an  ethereal  medium  on  tlie  other; 
and  a  few  experimental  facts  bearing  on  the  choice  between  such  hy- 
potheses had  been  ascertained. 

The  several  distinct  phenomena  of  common  reflexion  and  refrac- 
tion, of  double  refraction,  of  inflexion  or  diffraction,  and  of  the 
cqloured  rings,  did  not  seem  to  be  connected  by  any  common  princi- 
ple; nor,  even,  separately  considered,  could  it  be  said  that  they  were 
very  satisfactorily  explained.  It  was  now  the  peculiar  distinction  of 
Young  to  perceive,  and  to  establish  in  the  most  incontestable  manner, 
a  great  principle  of  the  simplest  kind,  which  at  once  rendered  the 
wave  hypothesis  applicable  to  the  two  last-named  classes  of  facts,  and 
thus  directly  connected  them  with  the  former. 

It  is  not  always  that  we  are  enabled  to  trace  the  first  rise  and  pro- 
gress of  the  idea  of  a  great  discovery  in  the  inventor's  mind.  We  can- 
not forbear  from  here  noticing,  that  Dr.  Young  has  left  on  record  the 
progress  of  the  first  suggestions  which  occurred  to  him  on  the  subject 
of  interference.  The  first  view  which  presented  itself  was  that  of  the 
analogies  furnished  by  sound,  which,  as  is  well  known,  is  conveyed  by 
means  of  waves  propagated  in  air.  And  in  the  case  of  two  sounds 
differing  a  very  little  from  the  same  pitch,  produced  at  the  same  time, 
we  have,  not  a  continuous  sound,  but  beats,  that  is,  alternations  of 
sound  and  silence;  the  waves  in  the  one  case  conspiring  with  and 
reinforcing  each  other,  in  the  other  counteracting,  neutralizing,  and 
destroying  each  other. 

But  in  more  special  reference  to  light.  Dr.  Young's  account  of  the 
origin  of  his  ideas  is  so  clear  and  striking  that  we  must  give  it  in  his 


304  THOMAS    YOUNG. 

Two    rays,   proceeding   from    the   same    source    by 
slightly  unequal  routes,  crossed  one  another  at   a  cer- 

own  words:  "  It  was  in  May,  1801,  that  I  discovered  by  reflecting  on 
the  beautiful  experiments  of  Newton,  a  law  which  appears  to  me  to 
account  for  a  greater  variety  of  interesting  phenomena  than  any  other 
optical  principle  that  has  yet  been  made  known.  I  shall  endeavour 
to  explain  this  law  by  a  comparison:  Suppose  a  number  of  equal 
waves  of  water  to  move  upon  the  surface  of  a  stagnant  lake,  with  a 
certain  constant  velocity,  and  to  enter  a  narrow  channel  leading  out 
of  the  lake; — suppose,  then,  another  similar  cause  to  have  excited 
another  equal  series  of  waves,  which  arrive  at  the  same  channel  with 
the  same  velocity,  and  at  the  same  time  with  the  first.  Neither  series 
of  waves  will  destroy  the  other,  but  their  effects  will  be  combined;  if 
they  enter  the  channel  in  such  a  manner  that  the  elevations  of  the  one 
series  coincide  with  those  of  the  other,  they  must  together  produce  a 
series  of  greater  joint  elevations;  but  if  the  elevations  of  one  series 
are  so  situated  as  to  correspond  to  the  depressions  of  the  other,  they 
must  exactly  fill  up  those  depressions,  and  the  surface  of  the  water 
must  remain  smooth;  at  least,  I  can  discover  no  alternative,  either 
from  theory  or  from  experiment.  Now,  I  maintain  that  similar  efiects 
take  place  whenever  two  portions  of  light  are  thus  mixed;  and  this  I 
call  the  general  law  of  the  interference  of  light."  i — Translator. 

For  the  sake  of  many  readers,  it  may  not  be  superfluous  or  useless 
here  briefly  to  illustrate  the  application  of  these  theoretical  ideas. 
We  have  only  to  imagins  in  like  manner,  in  the  case  of  the  rays  of 
light,  two  sets  of  waves  propagated  through  an  ethereal  medium  and 
coinciding  in  direction,  when  it  will  be  easily  apparent  that  just  as  in 
the  case  of  the  supposed  canal,  they  may  have  their  waves  either 
conspiring  or  counteracting,  and  consequently  giving  a  point  of  bright- 
ness or  darkness  accordingly. 

Thus,  a  coincidence  in  the  periods,  or  an  interval  of  an  integer  num- 
ber of  entire  wave-lengths,  would  cause  the  two  sj'stems  of  waves  to 
conspire  and  reinforce  each  other;  a  diflereuce  of  periods  of  half  a 
wave-length,  or  any  odd  number  of  half  wave-lengths,  would  cause 
the  two  systems  to  counteract  or  neutralize  each  other.  Thus, 
according  to  the  thickness,  there  would  be  a  point  of  darkness  or  of 
brightness  for  each  primary  ray,  and  the  succession  of  tints  would 
be  perfectly  explained. 

This  would  directlj'  apply  to  the  tliinjilms.  A  ray  impinging  would 
be  partly  reflected  at  the  first  surface  of  the  thin  film,  partly  entering 

1  Works,  vol.  i.  p.  202. 


INTERFERENCE    OF    LIGHT. 


305 


tain  point  in  gpace.  At  this  point  was  placed  a  sheet  of 
white  paper.     Each  ray,  taken  by  itself,  made  the  paper 

it  would  be  reflected  internally  at  its  second  surface,  and  emerge 
coinciding  in  direction  with  the  first,  but  retarded  behind  it  from  the 
thickness  traversed  in  its  undulations  either  by  a  whole,  or  half 
undulation,  or  some  multiples  of  these,— thus  giving  either  a  point  of 
brightness  or  one  of  darkness  accordingly;  or  by  some  intermediate 
fraction,  giving  an  intermediate  shade.  And  this  would  go  on  alter- 
nately at  successively  greater  thicknesses  of  the  film,  giving  a  suc- 
cession of  such  points  or  bands. 


Thus  at  two  successive  thicknesses  of  the  plate  (p),  the  incident 
rays  falling  on  it  in  parallel  directions,  i  i,  are  reflected  partially  from 
the  first  surface,  r  r,  and  partially  from  the  second,  rl  r'.  According 
to  the  diflerence  of  thickness  traversed,  these  may  be  in  accordance 
giving  a  point  of  brightness  as  at  +,  or  in  discordance  giving  a  point 
of  darkness  as  at  °. 

If  two  rays  or  sets  of  waves,  instead  of  being  exactly  superimposed 
be  supposed  to  meet  inclined  at  a  very  acute  angle,  in  a  somewhat 
similar  way  they  would,  at  a  series  of  points,  alternately  conspire  or 
clash  with  each  other,  thus  giving  rise  to  a  series  of  bright  and  dark 
points,  the  assemblage  of  which  will  pi-oduce  bands  or  stripes  on  a 
screen  intercepting  the  rays.  Now  as  to  actual  experimental  cases, 
it  was  in  the  application  of  this  latter  theoretical  idea  that  the  inven- 
tion of  Dr.  Young  was  peculiarly  displayed.  The  former  case  was 
that  alone  which  seems  to  have  occurred  to  Hooke  in  reference  to  the 
colours  of  thin  plates,  and  even  this  was  in  his  mind  but  a  very  indefi- 
nite conception;  nor  did  it  seem  at  first  sight  readiU' comparable  with 
such  cases  as  the  difl'raction  fringes,  or  still  less  with  the  internal 
bands  of  a  shadow  observed  by  Grimakli.  If  Hooke  had  imagined 
anv  theoretical  views  of  this  kind,  it  was   probably  confined  to  the 


30G 


THOMAS    YOUNG. 


more  bright  at  that  point,  but  when  the  two  rays  united 
and  arrived  at  that  point  together,  all  brightness  dis- 
appeared ;  complete  night  succeeded  to  day. 

one  case  of  the  thin  films;  Young's  great  merit  was  the  comprehen- 
siveness of  his  principle;  and  in  following  out  the  investigation,  he 
proceeded  at  once  to  such  a  generalization  as  evinced  that  compre- 
hensiveness and  connected  immediately  those  classes  of  phenomena 
apparently  so  different  in  character,— the  thin  films,  the  internal 
bands,  and  the  external  fringes.     When,  as  in  Grimaldi's  experiment 


/-since  called  the  phenomena  of  diffraction),  a  narrow  slip  of  card  was 
placed  in  a  very  narrow  beam  of  solar  light,  dark  and  bright  stripes 
parallel  to  the  sides  internally -marked  the  whole  shadow  longitudi- 
nally, while  the  external  fringes  appeared  on  the  outside  at  each  edge. 
The  general  appearance  of  the  shadow  of  a  long  narrow  body  with 
parallel  sides  in  a  beam  of  solar  light  issuing  from  a  minute  hole  in  a 
shutter,  or,  what  is  better,  the  focus  of  a  small  lens  collecting  the 
rays  to  a  point,  is  that  of  a  shadow  marked  witli  longitudinal  stripes 
and  externally  bordered  by  parallel  fringes  or  bands  of  liglit  slightly 
coloured,  as  seen  in  the  annexed  figure. 


DIFFRACTION. 


307 


Two  rays  do  not  always  annihilate  each  other  com- 
pletely at    their    point  of  intersection.     Sometimes    we 

To  exhibit  these  appearances  ordinarily  requires  the  sun's  light. 
But  the  translator  has  found  a  very  simple  method  of  exhibiting  these 
phenomena  on  a  minute  scale  by  candle  light,  by  merely  placing  a 
fine  wire  across  one  surface  of  a  lens  of  short  focus,  and  loolting 
through  it  at  light  admitted  through  a  narrow  slit  parallel  to  the  wire, 
or  even  the  flame  of  a  candle  at  a  considerable  distance. 

Next,  as  to  the  theoretical  explanation,  an  inspection  of  the  accom- 
panying diagram  will  perhaps  help  to  convey  an  idea  of  the  manner 
in  which  the  sevei'al  sets  of  waves  are  formed  and  iuterfere  in  the  case 
now  supposed. 

Young  conceived  the  beam  of  light  as  a  series  of  waves  propagated 
onward,  till,  on  reaching  the  card,  they  were  broken  up  into  two  new 
sets  of  waves  spreading  in  circles  round  each  edge  as  a  new  centre, 
while  part  of  the  original  set  continued  to  pass  on  at  each  side.  On 
the  principle  just  mentioned  these  would  interfere  with  the  new  por- 
tions on  the  outside;  and  the  two  new  portions  would  interfere  with 


308 


THOMAS    YOUNG. 


observe  only  a  partial  weakening  of  intensity,  sometimes, 
on  the  other  hand,  the  rays  conspire  and  increase  the 
illumination.  Every  thing  depends  on  the  difference  in 
the  length  of  route  which  they  have  gone  through,  and 


each  other  in  the  inside  of  the  shadow;  In  either  case  giving  stripes 
or  bands.  To  complete  the  proof,  when  an  opaque  screen  was  phiced 
so  as  to  intercept  the  rays  on  one  side,  though  abundance  of  light  was 
present  on  the  other,  yet  all  the  internal  bands  immediately  disap- 
peared; demonstrating  that  the  effect  was  due  solely  to  the  concur- 
rence of  the  light  from  both  sides.  The  bands  produced  by  light 
admitted  through  narrow  apertures,  and  numerous  other  phenomena 
of  the  same  kind,  may  receive  a  general  and  popular  explanation  in 
the  same  way. —  Translator. 


PERIODICAL    COLOURS.  309 

that,  according  to  very  simple  laws,  the  discovery  of 
which  in  any  age  would  suffice  to  immortalize  a  physi- 
cist. 

The  differences  of  route  which  produce  these  conflicts 
between  the  rays,  accompanied  hy  their  entire  mutual 
destruction,  have  not  the  same  numerical  value  for  the 
differently  coloured  primary  rays.  When  two  white  rays 
cross,  it  is  then  possible  that  one  of  their  chief  constituent 
parts,  tlie  red,  for  example,  may  alone  be  in  the  condition 
fit  for  mutual  destruction.  But  white,  deprived  of  its 
red,  becomes  green  !  Thus  intei'ference  of  light  mani- 
fests itself  in  the  phenomena  of  coloration.  Thus  the 
different  elementary  colours  are  placed  in  evidence  with- 
out any  prism  to  sei)arate  them.  We  should,  however, 
remark  that  there  does  not  exist  a  single  point  in  space 
where  a  thousand  rays  of  the  same  origin  do  not  proceed 
to  cross  one  another  after  reflexions  more  or  less  oblique, 
and  we  shall  perceive  at  a  glance  the  whole  extent  of 
the  unexplored  region  which  interferences  open  to  the 
investigations  of  experimenters. 

When  Young  published  this  theory,  many  phenomena 
of  periodical  colours  had  been  already  ofi"ered  to  the  no- 
tice of  observers  ;  and  we  should  add,  had  resisted  all 
attempts  at  explanation.  Among  the  number  we  mio-ht 
instance  the  coloured  rings  which  are  formed  by  reflexion, 
not  on  thin  films,  but  on  mirrors  of  thick  glass  slightly 
concave ;  the  irridescent  bands  of  different  breadths  with 
which  the  shadows  of  bodies  are  bordered  on  the  outside, 
and  in  some  instances  covered  within,  which  Grimaldi 
first  noticed,  and  which  afterwards  uselessly  exercised 
the  genius  of  Newton,  and  of  which  the  completion  of 
the  theory  was  reserved  for  Fresnel ;  the  bows  coloured 
red  and  green,  which  are  perceived  in  greater  or  less 


310  THOMAS    YOUNG. 

number  immediately  under  the  innermost  of  the  prismatic 
bands  of  the  rainbow,*  and  wliich  seemed  so  completely 
inexplicable,  that  the  writers  of  elementary  books  on 
physics  had  given  up  making  mention  of  them  ;  and  lastly, 
the  "coronas,"  or  broad  coloured  circles  with  varying 
diameters,  which  often  appear  surrounding  the  sun  and 
moon. 

If  I  call  to  mind  how  many  persons  do  not  appreciate 
scientific  theories,  except  in  proportion  to  the  immediate 
applications  which  they  may  otfei-,  I  cannot  terminate 
this  enumeration  of  the  phenomena  which  characterize 
the  several  series  of  more  or  less  numerous  periodical 
colours,  Avithout  mentioning  the  rings,  so  remarkable  by 
their  regularity  of  form  and  purity  of  tint  with  which 
every  brilliant  light  appears  surrounded,  when  we  look 
at  it  through  a  mass  of  fine  molecules  or  filaments  of 
equal  dimensions.  These  rings,  in  fact,  suggested  to 
Young  the  idea  of  an  instrument,  extremely  simple, 
which  he  called  an  "  eriometer,"  and  with  which  we 
can  measure  without  difficulty  the  dimensions  of  the  most 
minute  bodies.  The  eriometer,  as  yet  so  little  known  to 
observers,  has  an  immense  advantage  over  the  mici'o- 
scope  in  giving  at  a  single  glance  the  mean  magnitude  of 
millions  of  particles  which  are  contained  in  the  field  of 
view.  It  possesses,  moreover,  the  singular  property  of 
remaining  silent  when  the  particles  differ  much  in  mag- 
nitude among  themselves,  or,  in  other  words,  when  the 
question  of  determining  their  dimensions  has  no  real 
meaning. 

Young  applied  his  eriometer  to  the  measurement  of 
the  globules  of  blood  in  different  classes  of  animals, — to 

*  This  explanation  has  been  recently  controverted  by  Professor 
Potter.— P/ij7os.  Mag.  May,  1855. 


ERIOMETER.  311 

that  of  powders  furnished  by  different  species  of  vegeta- 
bles, of  the  fineness  of  different  kinds  of  fur  used  in  the 
manufacture  of  different  fabrics,  from  tliat  of  tlie  beaver, 
the  most  valuable  of  all,  down  to  that  of  the  common 
sheep  of  the  Sussex  breed,  which  stands  at  the  other 
extremity  of  the  scale,  and  is  composed  of  filaments  four 
times  and  a  half  thicker  than  that  of  the  beaver. 

Before  the  researches  of  Young,  the  numerous  phe- 
nomena of  colours*  Avhich  I  have  just  pointed  out  were 
not  only  inexplicable,  but  nothing  had  been  found  to 
connect  them  with  each  other.  Newton,  who  was  long 
engaged  on  the  subject,  had  not  perceived  any  connection 
between  the  rings  in  thin  films  and  the  bands  of  diffrac- 
tion. Young  reduced  these  two  kinds  of  coloured  bands 
alike  to  the  law  of  interference.  At  a  later  period,  when 
the  coloured  phenomena  of  polarization  had  been  discov- 
ered, he  observed,  in  certain  measures  of  the  thicknesses 
at  which  they  occurred,  some  remarkable  numerical  analo- 
gies, Avhich  made  it  very  reasonable  to  expect  that  sooner 
or  later  this  singular  kind  of  polarization  would  be  found 
connected  with  his  doctrine.  He  had  in  this  instance, 
however,  we  must  admit,  a  very  wide  hiatus  to  fill  up. 
The  knowledge  of  some  important  properties  of  light, 
then  completely  unknown,  would  have  been  necessary  to 
permit  him  to  conceive  the  whole  singularity  of  the  effects 
which  in  certain  crystals,  cut  in  certain  directions,  double 

*  Every  one  may  have  remarked  the  threads  of  a  spider's  web  occa- 
sionally exhibiting  brilliant  colours  in  the  sunshine.  The  same  thing 
is  seen  in  fine  scratches  on  the  surface  of  polished  metal,  produced  in 
a  more  regular  way,  by  the  fine  engraved  parallel  grooves  in  Barton's 
buttons.  The  colours  of  mother-of-pearl  are  of  the  same  kind;  all 
these  colours  Dr.  Young  showed  were  due  to  interference  of  the  por- 
tions of  light  reflected  from  the  sides  of  the  narrow  transparent  thread 
or  groove. —  Translator. 


312  THOMAS    YOUNG. 

refraction  produces  by  the  destruction  of  light  resuUiiig 
from  the  interference  of  rays ;  but  it  is  to  Young  that  the 
honour  belongs  of  having  opened  the  way  ;  it  was  he 
who  was  the  first  to  decypher  these  hieroglyphics  of 
optics.* 

*  It  has  been  well  observed  that  simplicity  is  not  always  a  fruit 
of  the  first  growth,  and  accordingly  some  of  the  earliest  of  Young's 
researches  were  complicated  by  unnecessary  conditions.  Thus,  to 
exhibit  the  effect  of  two  rays  interfering,  he  at  first  not  unnaturally 
transmitted  the  narrow  beam  of  light  through  two  small  apertures  near 
together.  In  point  of  fact,  though  the  real  effect  is  liere  seen,  it  is 
mixed  up  with  others  of  a  more  complex  kind.  The  narrow  apertures 
each  exhibited  coloured  fringes,  in  addition  to  the  interference  stripes 
seen  between  them.  The  coloured  fringes  of  apertures  (unless  very 
wide)  are  distinct  from  those  formed  by  one  external  edge  of  an  9paque 
body ;  the  light  from  each  side  conspires  to  the  effect  in  a  somewhat 
complex  manner.  If  the  aperture  be  otherwise  than  long  with  parallel 
sides,  the  phenomenon  becomes  still  more  complex,  and  the  calcula- 
tion difficult;  few  such  cases  have  ever  yet  been  solved,  and  some  such 
cases  have  been  dwelt  upon  as  formidable  objections  to  the  theory; 
they  are  simply  cases  to  which  the  formula,  from  its  mathematical 
difficulties,  has  not  yet  been  extended. 

In  all  these  cases  of  diffraction  an  opaque  body  was  used,  and  it 
might  still  be  suspected  that  some  action  of  the  edge  of  that  body  might 
be  concerned  in  the  result.  Numerous  experiments  of  Maraldi,  Dutour, 
Biot,  and  others,  were  directed  to  the  investigation  of  this  point.  Biot 
showed  that  an  opaque  body  was  not  necessary,  inasmuch  as  the  edge 
of  a  plate  of  glass,  or  even  the  bounding  line  of  two  fiices  of  a  glass  cut 
at  a  slight  inclination  to  each  other,  gave  the  same  fringes;  indeed, 
Newton  also  had  noticed  something  of  the  kind.  Haldat  varied  the 
conditions  of  the  edge  in  every  conceivable  way,  whether  of  form  or 
nature,  by  the  influence  of  magnetism,  galvanism,  electricity,  or  tem- 
perature from  freezing  to  a  red  heat,  without  producing  the  slightest 
difference  in  the  fringes;  a  result  which  it  would  be  impossible  to  con- 
ceive compatible  with  any  idea  of  an  atmosphere  of  attraction  or  repul- 
sion surrounding  the  edge. 

Again,  though  we  have  given  the  explanation  of  the  external  fringes 
in  its  simple  and  correct  form,  yet  both  Young  and  Fresnel  failed  in 
the  first  instance  to  see  it  in  that  light,  both  believing  that  the  reflexion 
of  a  portion  of  rays  from  the  edge  of  the  opaque  body  was  mainly  con- 
cerned in  producing  the  interference.    Subsequent  experiments  showed 


HIEROGLYPHICS.  313 


EGYPTIAN    HIEROGLYPHICS. HISTORY    OF    THE    FIRST 

EXACT   INTERPRETATION    GIVEN    OF    THEM. 

The  word  hieroglyphic,  regarded  not  metaphysically, 
but  in  its  natural  acceptation,  carries  us  into  a  field  which 

that  even  in  cases  where  that  edge  reflects  any  sensible  amount  of 
light,  its  influence  on  the  diftVacted  fringes  is  quite  inappreciable.  In 
fact,  Young,  in  a  letter  to  Fresnel,  in  returning  thanks  for  a  copy  of  a 
later  memoir  in  which  he  had  shown  this  suiiposition  to  be  unneces- 
sarj',  also  concui's  in  abandoning  it.  It  did  but  complicate  and  injure 
the  beauty  of  the  result. ^  And  every  doubt  must  have  disappeared  in 
the  minds  of  those  who  compared  the  minute  arithmetical  accuracy 
with  which  the  places  of  the  fringes,  as  computed  from  the  simple 
theory  in  the  investigations  of  Fresnel,  agreed  with  those  actually  de- 
termined by  the  nicest  micrometical  measurements. 

In  enumerating  the  discoveries  of  Young  in  the  first  establishment 
of  the  wave  theory,  it  is  somewhat  singular  that  Arago  (whether  from 
accident  or  design)  should  have  overlooked  one  investigation  which 
must  be  regarded  as  among  the  most  important.  The  great  support 
which  the  emission  theory  received  in  recent  times  was  that  derived 
from  Laplace's  memoir  on  the  law  of  double  refraction  (1809),  in 
which,  on  the  principle  of  "least  action,"  as  maintained  by  Mauper- 
tuis  and  applied  to  the  idea  of  luminous  molecules,  he  explained  the 
observed  laws  of  ordinary  and  extraordinary  refraction  in  Iceland  spar. 
This  investigation  exercised  a  powerful  influence  in  favor  of  the  mole- 
cular theory  over  the  minds  of  the  men  of  science  in  France  who  bowed 
implicitly  to  the  authority  of  Laplace.  But  the  memoir  of  Laplace  was 
the  subject  of  a  very  powerful  attack  on  the  part  of  Dr.  Young,  carried 
on  in  an  article  in  the  Quarterly  lieview,  November,  1809,  in  which  he 
disputed  the  mechanical  and  mathematical  grounds  of  Laplace's  the- 
ory, and  showed  that  the  same  laws  of  double  refraction  could  be  far 
more  easily  deduced  from  the  unduiatory  hypothesis.  Next  to  the 
discovery  of  interference,  this  refutation  of  the  strongest  point  of  the 
emission  theory  cannot  but  be  regarded  as  one  of  the  most  material  in 
the  development  and  establishment  of  the  unduiatory  view. 

To  the  statement  of  these  various  cases  of  interference  it  should  be 
added  that  when  the  tints  of  polarized  light  were  discovered.  Young 
in  1814,  applied  to  the  phenomena  the  f/encrcd  consideration  of  iwie?'- 

1  Young's  Works,  i.  393. 

BEC.    8ER.  14 


314  THOMAS    YOUNG. 

has  been  long  the  theatre  of  numerous  and  animated  de- 
bates. I  have  hesitated  whether  to  risk  offending  the 
feelings  which  tliis  question  has  excited.  The  secretary 
of  an  Academy  occupied  exclusively  with  the  exact 
sciences,  might  indeed,  without  impropriety,  remit  this 
philological  subject  to  other  more  competent  judges.  I 
also  feared,  I  will  avow,  to  find  myself  in  disagreement 
on  several  important  points  with  the  illustrious  man  of 
science  whose  labours  it  has  been  so  delightful  for  me  to 
analyze,  without  having  to  add  a  word  of  criticism  from 
my  pen.  All  these  scruples,  however,  vanish  when  I  re- 
flect that  the  interpretation  of  hieroglyphics  has  been  one 
of  the  most  beautiful  discoveries  of  our  age  ;  that  Young 
himself  has  mixed  up  my  name  with  discussions  relating 
to  it ;  that  to  examine  whether  France  can  jiretend  to 
this  new  title  to  glory,  is  to  enhance  the  importance  of 
the  task,  confided  to  me  at  this  moment,  and  to  perform 
the  duty  of  a  good  citizen.  I  am  aware  that  some  may 
find  narrowness  in  these  sentiments.  I  am  not  ignorant 
that  the  cosmopolitan  spirit  has  its  good  side  ;  but  with 
what  name  shall  I  stigmatize  it,  if,  when  all  neighbouring 

ference,  that  is  to  say,  he  showed  that  owing  to  the  differing  obliquities 
of  the  paths  of  the  rays  within  the  crystal  they  would  be  unequally 
retarded  in  their  passage,  and  would  consequently  emerge  in  condi- 
tions, with  regard  to  length  of  route,  respectively  of  accordance  or  dis- 
cordance at  corresponding  distances  round  the  centre  line  or  axis  of 
the  crystal,  and  thus  might  give  rise  to  coloured  rings.  Arago,  how- 
ever, soon  noticed  that  the  explanation  was  incomplete ;  the  main  point 
in  fact  remained  to  be  accounted  for,  viz:  why  we  see  no  colours  till 
the  analyzer  is  applied,  and  why  even  the  previous  polarization  is 
necessary  to  the  result.  It  was  not  until  about  two  years  afterwards 
that  Arago  and  Fresnel  jointly  succeeded  in  discovering  a  new  law, 
which  not  only  furnished  the  complete  solution  of  the  polarized  rings, 
but  at  length  cleared  away  all  the  difficulties  which  from  the  first  had 
surrounded  the  idea  of  polarization  itself  For  an  account  of  this  .-iee 
memoir  of  Fresnel. —  Trandatar. 


UIEROGLYPHICS.  315 

nations  enumerate  with  triumph  the  discoveries  of  their 
sons,  it  should  hinder  me  from  seeking,  even  in  the  pres- 
ent circle,  among  those  colleagues  whose  modesty  I  would 
not  hurt,  the  proof  that  France  is  not  degenerate ;  that 
she  also  adds  every  year  her  glorious  contingent  to  the 
vast  deposit  of  human  knowledge.* 

I  approach,  then,  the  question  of  Egyptian  writing, 
and  I  do  so  free  from  all  prejudice,  with  the  firm  wish 
of  being  just ;  with  the  lively  desire  to  conciliate  the 
rival  pretensions  of  two  men  of  science  whose  premature 
death  has  been  to  all  Europe  a  legitimate  subject  of  re- 
gret. Lastly,  I  shall  not  in  this  discussion  on  hieroglyphics 
transgress  the  bounds  imposed  on  me  ;  happy  if  those 
who  listen  to  me,  and  whose  indulgence  I  ask,  may  find 
that  I  have  known  how  to  escape  the  influence  of  a  sub- 
ject whose  obscurity  is  proverbial. 

Men  have  imagined  two  systems  of  writing  entirely 
distinct.  One  is  that  employed  by  the  Chinese,  which  is 
the  system  of  hieroglyphics  ;  the  other,  at  present  in  use 
among  all  other  nations,  bears  the  name  of  the  alphabet- 
ical or  phonetic  system. 

The  Chinese  have  no  letters  projierly  so  called  :  the 
characters  which  they  use  in  writing  are  strictly  hiero- 

*  In  bringing  out  a  part  of  this  chapter  on  Egyptian  Hieroglyphics 
in  the  Annuaire  for  1836,  Arago  has  added:  "  Tlie  first  exact  inter- 
pretation which  has  been  given  of  Egyptian  hieroglyphics  will  cer- 
tainly talce  its  place  among  the  most  beautiful  discoveries  of  the  age. 
Besides,  after  the  animated  debates  to  which  it  has  given  birth,  every 
one  would  desire  to  know  whether  France  can  conscientiously  pretend 
to  this  new  title  to  glory.  Thus  the  importance  of  the  question,  and 
the  national  self-love  properly  understood,  unite  in  encouraging  me  to 
publish  the  result  of  a  minute  examination  to  which  I  have  devoted 
myself.  Can  I,  then,  be  blind  to  the  danger  which  there  always  is  in 
attempting  difficult  subjects  in  matters  which  we  have  not  made  the 
special  subject  of  our  studies  ?  " 


316  THOMAS    YOUNG. 

glyphics  ;  they  do  not  represent  soutids  or  articulations, 
but  idecis.  Thus  a  house  is  represented  by  a  unique  and 
special  character,  which  does  not  change  even  when  the 
Chinese  have  come  to  call  a  house,  in  their  spoken  lan- 
guage, by  a  nanae  totally  different  from  that  which  they 
formerly  pronounced.  Does  this  result  appear  surpris- 
ing ?  Imagine  the  case  of  our  cyphers,  which  are  also 
hieroglyphics  ;  the  idea  of  one  added  to  itself  seven  times 
is  expressed  everywhere  in  France,  in  England,  in  Spain, 
&c.,  by  the  aid  of  two  circles  placed  vertically  one  over 
the  other,  and  touching  in  one  point ;  but  in  looking  at 
this  hieroglyphic  sign  (8)  the  Frenchman  pronounces 
"  huit,"  the  Englishman  "  eight,"  the  Spaniard  "  ocho." 
No  one  is  ignorant  that  it  is  the  same  with  compound 
numbers.  Thus,  to  speak  briefly,  if  the  Chinese  idio- 
graphic  signs  were  generally  adopted,  as  the  Arabic 
numerals  are,  every  one  would  read  in  his  own  language 
the  works  which  they  presented  to  him,  without  the  need 
of  knowing  a  single  word  of  the  language  spoken  by  the 
authors  who  have  written  them. 

It  is  not  so  with  alphabetical  writing  : — 

"  He  who  first  taught  us  the  ingenious  art 
To  paint  our  words,  and  speak  them  to  our  eyes," 

having  made  the  capital  remark  that  all  words  of  a  spoken 
language,  even  the  most  rich,  are  compounded  of  a  very 
limited  number  of  elementary  articulate  sounds,  invented 
artificial  signs  or  letters  to  the  number  of  twenty-four 
or  thirty  to  represent  them.  By  the  aid  of  these  signs 
differently  combined  he  could  write  every  word  which 
struck  his  ear  even  without  knowing  the  meaning 
of  it. 

The  Chinese  or  hieroglyphic  writing  seems  to  be  the 
infancy  of  the  art.     It  is  not  always,  as  has  been  some- 


HIEROGLYPHICS.  317 

times  said,  that  to  learn  to  read  it,  even  in  China,  occu- 
pies the  whole  life  of  a  studious  Mandarin.  Rerausat 
(whose  name  I  cannot  mention  without  recalling  one  of 
the  most  heavy  losses  which  literature  has  lately  sus- 
tained) has  established,  both  by  his  own  experience  and 
by  the  fact  of  the  excellent  scholars  he  has  formed  every 
year  by  his  lectures,  that  we  may  learn  Chinese  like  any 
other  language.  It  is  not  true,  as  was  once  imagined, 
that  the  characters  are  appropriated  solely  to  the  expres- 
sion of  common  ideas  ;  several  pages  of  the  romance  of 
Yu-kiao-li,  or  the  Two  Cousins,  will  suffice  to  show  that 
the  most  subtle  abstractions,  the  quintessence  of  refine- 
ments, are  not  beyond  the  range  of  the  Chinese  writing. 
The  chief  fault  of  this  mode  of  writing  is,  that  it  gives  no 
means  of  expressing  new  names.  A  letter  from  Canton 
might  have  told  at  Pekin,  that  on  the  14th  of  June,  1800, 
a  great  and  memorable  battle  saved  France  from  great 
peril ;  but  it  would  not  have  been  able  to  express  in  these 
purely  hieroglyphic  characters  that  this  glorious  event 
took  place  near  the  village  of  Marengo,  or  that  the  vic- 
torious general  was  called  Bonaparte.  A  people  among 
whom  the  communication  of  proper  names,  from  one  place 
to  another,  could  only  take  place  by  means  of  special 
messengers,  would  be,  as  we  see,  only  in  the  first  rudi- 
ments of  civilization.  These  preliminary  remarks  are 
not  useless.  The  question  of  priority,  which  the  graphic 
methods  of  Egypt  have  called  forth,  thus  come  to  be  easy 
to  explain  and  to  comprehend.  As  we  proceed,  in  fact, 
we  find  in  the  hieroglyphics  of  the  ancient  people  of  the 
Pharaohs,  all  the  artifices  of  which  the  Chinese  make  use 
at  the  pi'esent  day. 

Many  passages  of  Herodotus,  of  Diodorus  Siculus,  of 
Clement  of  Alexandria,  have  taught  us  that  the  Egyp- 


318  THOMAS    YOUNG. 

tians  had  two  or  three  different  sorts  of  wi-iting,  and  that 
in  one  of  these,  at  least,  symbolic  characters,  or  the  rep- 
resentatives of  ideas,  played  a  principal  part.  Horapollon 
has  even  preserved  to  us  the  signification  of  a  certain 
number  of  these  characters.  Thus  we  know  that  the 
/iaw^' designated  the  soul;  the  this,  the  heart;  the  dove 
(which  might  seem  strange),  a  violent  man  ;  the  Jlute, 
an  alien  ;  the  number  six,  pleasure  ;  a.  frog,  an  imprudent 
man  ;  the  ant,  wisdom  ;  a  running  knot,  love,  &c. 

The  signs  thus  preserved  by  Horapollon  form  only  a 
very  small  part  of  the  eight  or  nine  hundred  characters 
which  have  been  found  in  the  ancient  inscriptions.  The 
moderns,  Kircher  among  others,  have  endeavoured  to 
enlarge  the  number.  Their  efforts  have  not  given  any 
useful  result,  unless  it  be  so  to  show  to  what  errors  even 
the  best  instructed  men  expose  themselves  when,  in  the 
search  after  facts,  they  abandon  themselves  without  re- 
straint to  imagination.  In  the  want  of  data,  the  inter- 
pretation of  the  Egyptian  writings  appeared  for  a  long 
time,  to  all  sound  minds,  a  problem  completely  incapable 
of  solution  ;  when  in  1799,  M.  Boussard,  an  engineer 
officer,  discovered  in  the  excavations  which  he  was  making 
near  Rosetta,  a  large  stone  covered  with  inscriptions  in 
three  kinds  of  characters  quite  distinct. 

One  of  the  series  of  characters  was  Greek.  This,  in 
spite  of  some  mutilations,  made  clearly  known  that  the  au- 
thors of  the  monument  had  ordained  that  the  same  inscrip- 
tion should  be  traced  in  three  different  sorts  of  characters, 
viz :  in  the  sacred  characters  or  Egyptian  hieroglyphics, 
in  the  local  or  vulgar  characters,  and  in  Greek.  Thus, 
by  an  unexpected  good  fortune,  the  philologists  found 
themselves  in  possession  of  a  Greek  text,  having  also 
before  them  its  translation  into  the  Egyptian  language, 


THE    ROSETTA    INSCRIPTION.  319 

or  at  least   a  transcription  in  two  sorts  of  characters,, 
anciently  in  use  on  the  banks  of  the  Nile. 

This  Rosetta  stone,  since  so  celebrated,  and  which  M. 
Boussard  presented  to  the  Institute  of  Cairo,  was  taken 
from  that  body  at  the  period  when  the  French  array 
evacuated  Egypt.  It  was  preserved,  however,  in  the 
British  Museum,  where  it  figured,  as  Thomas  Young 
said,  as  a  monument  of  British  valour.  Putting  valour 
out  of  the  question,  the  celebrated  philosopher  might 
have  added,  without  too  much  partiality,  that  this  invalu- 
able trilingual  monument  thus  bears  some  witness  to  the 
advanced  views  which  guided  all  the  details  of  the  mem- 
orable expedition  into  Egypt,  as  also  to  the  indefatigable 
zeal  of  the  distinguished  savants  whose  labours,  often 
carried  on  under  the  fire  of  the  forts,  have  added  so 
much  to  the  glory  of  their  country.  The  importance  of 
the  Rosetta  stone  struck  them,  in  fact,  so  forcibly,  that  in 
order  not  to  abandon  this  precious  treasure  to  the  adven- 
turous chances  of  a  sea  voyage,  they  earnestly  applied 
themselves,  from  the  first,  to  reproduce  it,  by  copies,  by  im- 
pressions taken  in  the  way  of  printings  from  engi-avings, 
by  moulds  in  plaster  or  sulphur.  We  must  add  that 
antiquaries  of  all  countries  became  first  acquainted  with 
the  Rosetta  stone  from  the  designs  given  by  the  French 
savants. 

One  of  the  most  illustrious  members  of  the  Institute,  M. 
Silvestre  de  Sacy,  entered  first  in  1802  on  the  career 
which  the  trilingual  inscription  opened  to  the  investiga- 
tions of  philologists.  He  only  occupied  himself  on  the 
Egyptian  text  in  common  characters.  He  there  discov- 
ered the  groups  which  represent  the  different  proper 
names,  and  their  phonetic  nature.  Thus  in  one  of  two 
inscriptions,  at   least,   the   Egyptians    had    the   signs   of 


320  THOMAS    YOUNG. 

sounds,  or  true  letters.  This  important  result  found  no 
opponents  after  a  Swedish  man  of  science,  M.  Akerblad, 
in  completing  the  labours  of  our  felloAV-countryman,  had 
assigned,  with  a  probability  bordering  on  certainty,  the 
phonetic  value  of  each  of  the  different  characters  em- 
ployed in  the  transcription  of  the  proper  names  which 
the  Greek  text  disclosed. 

There  remained,  all  along,  the  purely  hieroglyphic 
part  of  the  inscription,  or  what  was  supposed  such ; 
this  remained  untouched  ;  no  one  had  ventured  to  at- 
tempt to  decypher  it. 

It  is  here  that  we  find  Young  declaring,  as  if  by  a 
species  of  inspiration,  that  in  the  multitude  of  sculptured 
signs  on  the  stone  representing  either  entire  animals,  or 
fantastic  forms,  or  again  instruments,  products  of  art,  or 
geometrical  forms,  those  of  these  signs  which  were  found 
inclosed  in  elliptic  borders,  corresponded  to  the  proper 
names  in  the  Greek  inscription  ;  in  particular  to  the 
name  of  Ptolemy,  the  only  one  Avliich  in  the  hieroglyphic 
inscription  remains  uninjured.  Immediately  afterwards 
Young  said  that  in  the  special  case  of  the  border  or 
scroll,  the  signs  included  represented  no  longer  ideas, 
but  sounds.  In  a  word,  he  sought  by  a  minute  and  re- 
fined analysis  to  assign  an  individual  hieroglyphic  to 
each  of  the  sounds  which  the  ear  receives  in  the  name  of 
Ptolemy  in  the  Rosetta  stone,  and  in  that  of  Berenice,  in 
another  monument. 

Thus  we  see,  unless  I  mistake,  in  the  researches  of 
Young  on  the  graphic  systems  of  the  Egyi)tians,  the 
three  culminating  points.  No  one,  it  is  said,  had  per- 
ceived them,  or  at  least  had  pointed  them  out,  before  the 
English  philosopher.  This  opinion,  although  generally 
admitted,  appears  to  me  open  to  dispute.     It  is,  in  fact, 


THE    ROSETTA    INSCRIPTION.  321 

certain  tliat  in  1766  M.  de  Guignes,  in  a  printed  memoir, 
had  indicated  that  the  scrolls  in  Egyptian  inscriptions  in- 
chided  all  the  proper  names.  Every  one  might  also  see 
in  the  same  work  the  arguments  on  which  the  learned 
orientalist  relied  to  establish  the  opinion  which  he  had  em- 
braced on  the  constant  phonetic  character  of  the  Egyp- 
tian hieroglyphics.  Young  then  has  the  priority  on  this 
point  alone :  to  him  belongs  the  first  attempt  which  had 
been  made  to  decompose  in  letters  the  groups  of  the 
scrolls,  to  give  a  phonetic  value  to  the  hieroglyphics 
which  composed  in  the  stone  of  Rosetta  the  name  of 
Ptolemy. 

In  this  research,  as  we  might  expect.  Young  furnished 
new  proofs  of  his  immense  penetration  ;  but  misled  by  a 
false  system,  his  efforts  had  not  a  full  success.  Thus 
sometimes  he  attributes  to  the  hieroglyphic  characters  a 
value  simply  alphabetical,  further  on  he  gives  them  a 
value  which  is  syllabic  or  disyllabic,  without  being  struck 
by  what  must  seem  so  strange  in  this  mixture  of  different 
characters.  The  fragment  of  an  alphabet  published  by 
Young  includes  then  something  both  of  truth  and  false- 
hood ;  but  the  false  so  much  abounds  that  it  would  be 
impossible  to  apply  the  value  of  the  letters  which  com- 
pose it  to  any  other  reading  than  that  of  the  two  proper 
names  from  which  it  was  derived.  The  word  impossible 
is  so  rarely  met  with  in  the  scientific  career  of  Young, 
that  I  must  hasten  to  justify  it.  I  will  say  then  that  after 
the  composition  of  his  alphabet  Young  himself  believed 
that  he  saw  in  the  scroll  of  an  Egyptian  monument  the 
name  of  '■'■  Arsinoe,"  where  his  celebrated  competitor  had 
since  shown  with  irresistible  evidence  the  word  "auto- 
crator  ;"  that  he  believed  he  had  found  '■'■  euergetes"  in  a 
group  where  we  ought  to  read  '■'•Gcesar.'" 

14* 


322  THOMAS    YOUNG. 

The  labors  of  Champollion,  as  to  the  discovery  of  the 
phonetic  value  of  hieroglyphics,  are  clear,  distinct,  and 
cannot  involve  any  doubt.  Each  sign  is  equivalent  to  a 
single  vowel  or  consonant.  Its  value  is  not  arbitrary  : 
every  phonetic  hieroglyphic  is  the  image  of  a  physical 
object  whose  name  in  the  Egyptian  language  commences 
with  the  vowel  or  the  consonant  which  it  is  wished  to 
represent.* 

The  alphabet  of  Champollion,  once  modelled  from  the 
Stone  of  Rosetta  and  two  or  three  other  monuments, 
enables  us  to  read  inscriptions  entirely  different  ;  for 
example,  the  name  of  Cleopatra  on  the  obelisk  of  Philoe, 
long  ago  transported  into  England,  and  -where  Dr.  Young, 
armed  with  his  alphabet,  could  discover  nothing.  On  the 
temple  of  Karnac,  Champollion  read  twice  the  name  of 
Alexander  :  on  the  Zodiac  of  Denderah,  the  title  of  a  Ro- 
man emperor ;  on  the  grand  edifice  above  which  it  is 
placed,  the  names  and  surnames  of  the  emperors  Augus- 

*  This  will  become  clear  to  every  one,  if  we  seek,  by  following  the 
Egyptian  system,  to  compose  hieroglyphics  in  the  French  language. 
A  may  be  represented  by  (agneau)  a  lamb;  (aigle)  an  eagle;  an  ass, 
anemone,  artichoke,  &c.  B  by  a  balance,  a  whale  (baleine);  a  boat, 
&c.  C  by  cabana  (badger);  cheval  (horse);  cat,  cedar,  &c.  E  by 
6p6e  (a  sword),  elephant,  epagneul  (spaniel),  &c.  Abb6  then  would 
be  written  in  French  hieroglyphics  by  putting  any  of  the  following 
figures  in  succession : — a  lamb,  a  balance,  a  whale,  an  elephant.  Or 
an  eagle,  a  boat,  a  sword,  &c. 

This  kind  of  writing  has  some  analogy,  as  we  see,  with  the  rebus  in 
which  confectioners  wrap  their  bonbons.  Thus  we  see  at  wha*  stage 
these  Egyptian  priests  were  of  whom  antiquity  has  so  much  boasted, 
but  who,  we  must  say,  have  taught  us  so  little. 

M.  Champollion  calls  Iwmoplwnes  all  those  signs  which,  representing 
the  same  sound  or  the  same  articulation,  can  be  substituted  indifl'er- 
ently  for  each  other.  In  the  actual  state  of  the  Egyptian  alphabet  I 
perceive  six  or  seven  homophone  signs  for  A,  and  more  than  twelve 
for  the  Greek  sigma. — Ara(jo. 


PHONETIC    SYSTEM.  323 

tus,  Tiberius,  Claudius,  Nero,  Domitian,  &c.  Thus,  to 
speak  briefly,  we  find,  on  one  hand,  the  lively  discussion, 
to  which  the  age  of  these  monuments  had  given  rise, 
completely  terminated  ;  on  the  other,  we  observe  it  estab- 
lished beyond  question  that  under  the  Roman  dominion 
hieroglyphics  were  still  in  full  use  on  the  banks  of  the 
Nile. 

The  alphabet  which  had  given  such  unhoped  for  re- 
sults, whether  appUed  to  the  great  Obelisks  at  Karnac, 
or  to  other  monuments  which  are  also  recognized  as  be- 
ing of  the  age  of  the  Pharaohs,  presents  to  us  the  names 
of  many  other  kings  of  this  ancient  race  ;  the  names  of 
Egyptian  deities  ;  we  can  say  more,  substantives,  adjec- 
tives, and  verbs  of  the  Coptic  language  :  Young  was 
then  deceived  when  he  regarded  the  phonetic  hiero- 
glyphics as  a  modern  invention  ;  when  he  advanced  that 
tliey  had  served  solely  for  the  transcription  of  proper 
names  Ibreigu  to  Egypt.  M.  de  Guignes,  and  above  all, 
M.  Etienne  Quatremere,  established,  on  the  contrary,  a 
real  fact  and  one  of  great  importance, — that  the  readino' 
of  the  inscriptions  of  the  Pharaohs  is  corroborated  by 
irresistible  proofs,  while  they  show  that  the  existing 
Coptic  language  was  that  of  the  ancient  subjects  of 
Sesostris. 

We  now  know  the  facts ;  I  may  then  confine  myself  to 
confirm,  by  a  few  short  observations,  the  consequences 
which  appear  to  me  to  result  from  them. 

Discussions  of  priority,  even  under  the  dominion  of 
national  prejudices,  will  have  become  embittered  if  they 
can  be  reduced  to  fixed  rules,  but  in  certain  cases  the 
first  idea  is  every  thing ;  in  others,  the  details  offer  the 
chief  difficulties  ;  sometimes  the  merit  seems  to  consist 
less  in  the  conception  of  a  theory  than  in  its  demonstra- 


324  .  THOMAS    YOUNG. 

tion.  We  then  infer  how  much  the  choice  of  a  particular 
point  of  view  must  depend  on  arbitrary  conditions  ;  and, 
lastly,  how  much  influence  it  will  have  on  the  definitive 
conclusion.  To  escape  from  these  embarrassments  I 
have  sought  an  example  in  which  the  parts  respectively 
played  by  two  rival  claimants  for  an  invention  may  be 
assimilated  to  those  of  Champollion  and  Young,  and 
which  has,  on  the  other  hand,  united  all  opinions.  This 
example,  I  believe,  I  have  found  in  the  Interferences, 
even  leaving  out  of  the  question,  as  regards  the  subject 
of  the  hieroglyphics,  the  quotations  from  the  memoir  of 
M.  de  Guignes.     It  is  as  follows  : — 

Hooke  in  fact  had  announced  before  Dr.  Young  that 
luminous  rays  interfered,  just  as  the  latter  had  asserted 
before  Champollion  that  the  Egyptian  hieroglyphics  are 
sometimes  phonetic.  Hooke  did  not  prove  directly  his 
hypothesis  ;  the  proof  of  the  phonetic  values  assigned  by 
Young  to  different  hieroglyphics  could  only  rest  on  read- 
ings which  had  not  as  yet  been  made  and  which  could 
not  then  be  made. 

From  want  of  knowing  the  composition  of  white  light, 
Hooke  had  not  an  exact  idea  of  the  nature  of  interfer- 
ences, as  Young  on  his  part  deceived  himself  by  an 
imagined  syllabic  or  dissyllabic  value  of  hieroglyphics. 

Young,  by  unanimous  consent,  is  regarded  as  the 
author  of  the  theory  of  interferences.  Thence,  by  a 
parity  of  reasoning  which  seems  to  me  inevitable,  Cham- 
pollion ought  to  be  regarded  as  the  author  of  the  discov- 
ery of  hieroglyphics. 

I  regret  not  to  have  sooner  thought  of  this  comparison. 
If  in  his  lifetime  Young  had  been  placed  in  the  alterna- 
tive of  being  the  originator  of  the  doctrine  of  inter- 
ferences, leaving  the  hieroglyphics  to  Champollion,  or  to 


Cl^AIMS    OF    YOUNG.  325 

keep  the  hieroglyphics,  giving  up  to  Hooke  the  ingenious 
optical  theory,  I  do  not  doubt  he  would  have  felt  obliged 
to  recognize  the  claims  of  our  illustrious  fellow-country- 
man. At  all  events  there  would  have  remained  with 
him,  what  no  one  could  have  contested,  the  right  to  ap- 
pear in  the  history  of  the  memorable  discovery  of  the 
interpretation  of  hieroglyphics  in  the  same  relative  posi- 
tion as  that  in  whicli  Kepler,  Borelli,  Hooke,  and  Wren 
appeared  in  the  History  of  Universal  Gravitation. 


NOTE. 

We  have  here  put  before  our  readers  the  literal  version  of 
Arago's  statement  respecting  the  claims  of  Young  in  regard 
to  the  discovery  of  the  principle  of  interpreting  the  Egyptian 
hieroglyphics.  Arago's  representations  have  been,  as  is  well 
known,  greatly  called  in  question.  And  though  he  through- 
out speaks  in  a  tone  of  marked  courtesy  and  candour  towards 
Young,  yet  it  is  clear  that  he  espouses  the  cause  of  Champol- 
lion  with  an  ardour  whicli  many,  in  this  country,  believe  has, 
in  some  degree,  blinded  him  to  the  truth  of  the  case. 

At  any  rate,  in  the  vivid  and  highly  coloured  sketch  here 
presented  by  M.  Arago,  the  reader  may  need  some  caution 
in  discriminating  the  fair  share  of  merit  which  may  be  claimed 
by  the  respective  parties  engaged  in  the  inquiry.  The  au- 
thor's national  partialities  may  very  naturally  have  had  some 
influence  in  biassing  his  judgment.  It  is  impossible  here  to 
enter  on  details  of  controversy.  But  both  as  to  the  actual 
amount  and  accuracy  of  Dr.  Young's  investigations  and  the 
relative  claims  of  M.  Champollion,  the  reader  may  find  it 
desirable  to  refer  to  the  extended  discussion  of  the  subject 
given  in  Dr.  Peacock's  Life  of  Young.  Without  the  preten- 
sion, or,  indeed,  the  possibility,  of  adequately  going  into  this 
question  within  the  limits  of  such  a  commentary  as  can  be  here 
given,  we  shall   content  ourselves  with  pointing  out  to  the 


326  THOMAS    VOUNG. 

notice  of  our  readers  a  few  of  those  passages  in  that  work  In 
which  Dr.  Young's  claims  are  so  powerfully  vindicated.  The 
conclusions  turn  on  such  a  variety  of  points  of  details  that  it 
would  be  wholly  impracticable  to  attempt  any  analysis  of 
them  in  this  place.  But  the  result  tends  to  assign  a  consid- 
erably larger  share  of  credit  in  the  discovery  to  Dr.  Young 
than  Arago  seems  disposed  to  allow  him.  Dr,  Peacock's  able 
and  elaborate  work  is  doubtless  in  the  hands  of  all  those  who 
take  any  interest  in  a  question  so  important  to  the  advance  of 
philological  and  ethnological  science  as  well  as  to  general  lit- 
erature. Yet  a  slight  sketch  of  the  chief  points  referred  to 
may  not  be  useless. 

We  may  first  mention  that  Dr.  Young's  article  "  Egypt " 
in  the  Supplement  to  the  Encyclopedia  Britannica,  published 
in  1819,  contains  the  most  comprehensive  survey  of  his  labours 
and  conclusions  on  the  subject  of  hieroglyphic  literature  up 
to  that  date.  It  does  not  profess  to  go  into  those  minutiaj  of 
critical  detail,  for  which  reference  must  be  made  to  his  nu- 
merous other  writings  on  the  subject.  But  as  a  general  and 
popular  view  it  will  always  be  consulted  with  advantage. 
Nevertheless,  the  reader  must  always  bear  in  mind  that,  in 
the  statements  thus  given,  much  had  to  be  revised,  or  even 
reversed,  fi'om  the  improved  disclosures  of  his  later  researches. 

Dr.  Peacock  has  alluded  but  briefly  to  the  views  of  Arago, 
and  towards  the  conclusion  of  the  chapter,  sums  up  the  repre- 
sentation of  the  case  as  given  in  the  eloge,  remarking  only 
that  the  whole  of  his  previous  statements  constitute  the  refu- 
tation of  it. 

The  following  extract  will  show  the  main  claims  of  Young, 
insisted  on  by  his  biographer. 

"  It  was  Dr.  Young  who  first  determined,  and  by  no  easy 
process,  that  the  '  rings '  *  on  the  Rosetta  stone  contained  the 
name  of  Ptolemy.  It  was  Dr.  Young  who  determined  that 
the  semicircle  and  oval,  found  at  the  end  of  the  second  ring, 

*  Certain  portions  of  the  hieroglyphical  characters  are  found  sur- 
rounded by  a  ring  or  enclosure  called  by  the  French  "  Cartouclies." 


CLAIMS    OF    YOUNG.  327 

in  connection  with  the  former,  was  expressive  of  the  feminine 
gender ;  and  it  was  Dr.  Young  who  had  not  only  first  suo-- 
gested  that  the  characters  in  the  ring  of  Ptolemy  were  pho- 
netic, but  had  determined,  with  one  very  unimportant  inac- 
curac}',  the  values  of  four  of  those  which  were  common  to  the 
name  of  Cleopatra,  which  were  required  to  be  analyzed.  All 
the  principles  involved  in  the  discovery  of  an  alphabet  of 
phonetic  hieroglyphics  were  not  only  distinctly  laid  down, 
but  fully  exemplified  by  him  ;  and  it  only  required  the  fur- 
ther identification  of  one  or  two  royal  names  with  the  rin<rs, 
which  expressed  them  in  hieroglyphics,  to  extend  the  alpha- 
bet already  known  sufficiently  to  bring  even  names  which 
were  not  already  identified  under  its  operation." 

Dr.  Peacock  states  that  ChampoUion  and  Young,  while 
engaged  simultaneously  in  the  prosecution  of  the  researches 
connected  with  these  points,  in  some  instances  had  opportu- 
nities of  personal  communication  with  each  other.  But 
ChampoUion  enjoyed  especial  advantages  from  circumstances 
which  placed  some  of  the  papyri  in  his  possession ;  and  thus 
enabled  him  to  take  precedence  in  the  publication  of  results, 
while  his  competitor,  if  he  had  enjoyed  the  same  facilities, 
would,  no  doubt,  have  been  equally  competent  to  perceive 
the  force  of  the  new  evidence  thus  adduced,  and  equally 
ready  to  make  use  of  it,  even  if  setting  aside  some  of  his 
early  inferences  and  conjectures. 

Dr.  Peacock,  after  reflecting  with  much  severity  on  Cham- 
poUion, expresses  his  regret  to  find  so  eminent  a  writer  as 
Chevalier  Bunsen,  whose  remarks  are  quoted  before,  (p.  311,) 
"  supporting,  by  the  weight  of  his  authority,  some  of  the 
grossest  of  these  misrepresentations"  (p.  337). 

Dr.  Young  displayed  singular  modesty  and  forbearance  in 
his  controversy  with  ChampoUion,  treating  him  throughout 
with  all  the  respect  due  to  his  acknowledged  eminence  ;  and 
while  mildly  reproaching  him  with  omitting  to  give  him  the 
due  credit  for  his  own  share  in  the  research,  yet  in  no  way 
insinuating  that  any  discreditable  motive  led  to  the  omission. 

Dr.  Peacock,  however,  thinks  a  far  more  stringent  tone  of 


328  THOMAS    YOUNG. 

criticism  might  have  been  faii-Iy  apphed ;  he  takes  up  the 
cause  of  Young  with  a  less  scrupulous  zeal ;  and  though  with 
perfect  good  temper,  yet  with  deeply  damaging  force  of  argu- 
ment and  statement  of  facts,  exposes  the  very  unjustifiable 
nature  of  Champollion's  assumptions,  and  vindicates  the 
claims  of  Young  to  his  fair  and  important  share  in  these  dis- 
coveries. 

He  dwells  on  the  tone  of  assumption  in  which  Champollion 
presents  himself  to  his  readers  as  in  exclusive  possession  of 
a  province  of  which  he  had  long  since  been  the  sole  con- 
queror, and  regards  every  question  raised  as  to  his  exclusive 
rights  as  an  unjustifiable  attack  to  be  resented  and  repelled ; 
while  he  studiously  suppresses  the  dates  of  the  successive 
stages  of  the  discovery,  and  thus  attacks  Young  on  the  asser- 
tions made  on  imperfect  knowledge  in  the  earlier  stages  of 
his  investigations,  with  the  aid  of  all  his  own  accumulated 
information  acquired  subsequently ;  a  proceeding  the  iniquity 
of  which  needs  only  stating  to  stand  exposed. 

As  instances  of  this,  it  is  mentioned  that  Young,  in  1816, 
on  the  strength  of  comparatively  imperfect  information  then 
acquired,  made  some  representations  respecting  the  enchorial 
characters  in  the  Rosetta  inscription,  and  their  relation  to 
those  employed  in  the  funereal  rolls.  These  Champollion 
criticizes  and  exposes  without  reserve,  from  the  more  full 
knowledge  he  had  obtained  in  1824  ;  entirely  passing  over 
Young's  own  later  statement  on  the  same  subject,  correcting 
his  former  views,  and  from  which  even  Dr.  Peacock  considers 
Champollion  himself  probably  derived  a  large  portion  of  his 
own  knowledge  of  the  subject ! 

Ur.  Peacock  has  collected,  in  one  point  of  view,  Champol- 
lion's main  assertions  as  representing  the  state  of  the  case. 
But  he  has  shown  that  some  of  the  propositions  dwelt  upon 
were,  in  point  of  fact,  never  maintained  by  Dr.  Young;  and 
it  was  chiefly  by  his  later  researches,  that  the  erroneous  im- 
pressions at  first  entertained,  respecting  the  points  to  which 
they  relate,  had  been  corrected,  and  their  true  nature  estab- 
lished. 


MISCELLANEOUS    WORKS    OF    YOUNG.  329 

In  1821,  ChampoUion  denied  altogether  the  existence  of 
an  alphabetic  element  among  the  hieroglyphics.  But  in  the 
following  year  he  adopted  the  whole  of  Young's  principles, 
and  applied  them  with  one  modification  only.  The  analogy 
of  certain  marks  in  the  Chinese  hieroglj^ohics,  to  signify 
proper  names,  the  principle  that  the  phonetic  power  of  the 
symbol  is  derived  from  the  initial  letter  or  syllable  of  the 
name  of  the  object  which  it  represents  in  the  Egyptian  lan- 
guage, are  among  the  chief  of  those  which  he  borrows  with- 
out acknowledgment,  or  claims  without  regard  to  their  prior 
announcement  by  Young.  "  It  would  be  difficult,"  says  Dr. 
Peacock,  "  to  point  out  in  the  history  of  Hterature  a  more 
flagrant  example  of  disingenuous  suppression  of  the  real  facts 
bearing  on  an  important  discovery. —  Translator. 


MISCELLANEOUS    WORKS    OF    DR.    YOUNG. 

The  limits  prescribed  do  not  permit  me  even  to  quote 
the  mere  titles  of  all  the  numerous  writings  which  Dr. 
Y^oung  published.  Nevei'theless,  the  public  reading  of 
so  rich  a  catalogue  would  certainly  have  sufficed  to 
establish  the  celebrity  of  our  colleague.  "Who  would  not 
imagine  in  fact  that  he  had  before  him  the  register  of 
the  labours  of  several  academies,  and  not  those  of  a  sin- 
gle individual,  on  hearing,  for  instance,  the  following  list 
of  titles  : — 

Memoir  on  the  Establishments  where  Iron  is  wrought. 
Essays  on  Music  and  Painting. 

Kem.arks  on  the  Habits  of  Spiders  and  the  Theory  of  Fabricius. 
On  the  Stability  of  the  Arches  of  Bridges. 
On  the  Atmosphere  of  the  Moon. 
Description  of  a  new  Species  of  Opercularia. 
Mathematical  theory  of  Epicycloidal  Curves. 
Restoration  and  Translation  of  different  Greek  Inscriptions. 
On  the  means  of  strengthening  the  Construction  of  Ships  of  the 
Line. 


330  THOMAS    YOUNG. 

On  the  play  of  the  Heart  and  of  the  Arteries  in  the  phenomena  of  ■ 
circuhition. 

Theory  of  Tides. 

On  the  Diseases  of  the  Chest. 

On  the  Friction  of  the  Axes  of  Machines. 

On  the  Yellow  Fever. 

On  the  Calculation  of  Eclipses. 

Essays  on  Grammar,  &c.* 

CHARACTER  OF  YOUNG. — HIS  POSITION  AS  A  PHYSI- 
CIAN.  HIS  ENGAGEMENT  ON  THE  NAUTICAL  ALMA- 
NAC.  HIS    DEATH. 

Labours  so  numerous  and  varied  seem  as  if  they 
must  have  required  the  laborious  and  retired  life  of  that 
class  of  men  of  science,  which,  to  say  the  truth,  is  begin- 
ning to  disappear,  who  from  their  earliest  youth  separate 
themselves  from  their  companions  to  shut  themselves  up 
completely  in  their  studies.  Thomas  Young  was,  on  the 
contrary,  what  is  usually  called  a  man  of  the  world. 
He  constantly  frequented  the  best  society  in  London. 
The  graces  of  his  wit,  the  elegance  of  his  manners,  were 
amply  sufficient  to  make  him  remarkable.  But  when 
we  figure  to  ourselves  those  numerous  assemblies  in 
which  fifty  different  subjects  in  turn  are  skimmed  over 
in  a  few  minutes,  we  may  conceive  what  value  would  be 
attached  to  one  who  was  a  true  living  library,  from  whom 
every  one  could  find,  at  the  moment,  an  exact,  precise, 
substantial  answer  on  all  kinds  of  questions  which  they 
could  propose  to  him.  Young  was  much  occupied  with 
the  fine  arts.     Many  of  his  memoirs  testify  the  profound 

*  This  list,  it  should  be  borne  in  mind,  is  intended  by  the  author 
merely  as  a  specimen  of  the  vast  catalogue  which  might  be  made  of 
Young's  writings ;  the  reader  will  find  ample  details  as  to  his  innu- 
merable pTOductions  in  Peacock's  Life. —  Translator. 


CHARACTKR    AND    ATTAINMKNTS.  331 

knowledge  which  he  had  happily  acquired  of  the  theory 
of  music.  He  carried  out  also  to  a  great  extent  the  tal- 
ent of  executing  it ;  and  I  believe  it  is  certain  that  of  all 
known  instruments,  even  including  the  Scottish  bagpipe, 
only  one  or  two  could  be  named  on  which  he  could  not 
play.  His  taste  for  painting  developed  itself  during  a 
visit  which  he  paid  to  Germany.  There  the  magnificent 
collection  of  Dresden  absorbed  his  attention  entirely  ;  for 
he  aspired  not  solely  to  the  easy  credit  of  connecting 
together,  without  mistake,  the  name  of  such  or  such  an 
artist  with  such  or  such  a  painting ;  the  defects  and  the 
characteristic  qualities  of  the  greatest  masters,  their  fre- 
quent changes  of  manner,  the  material  objects  which 
they  introduced  into  their  works,  the  modifications  which 
those  objects  and  the  colours  underwent  in  progress  of 
time,  among  other  points,  occupied  him  in  succession. 
Young,  in  one  word,  studied  painting  in  Saxony,  as  he 
had  before  studied  languages  in  his  own  country,  and  as 
he  afterwards  studied  the  sciences.  Every  thing,  in  fact, 
was  a  subject  of  meditation  and  research.  The  univer- 
sity contemporaries  of  the  illustrious  physicist  recalled  a 
laughable  instance  of  this  trait  of  his  mind.  They  re- 
lated that  entering  his  room  one  day,  when  for  the  first 
time  he  had  taken  a  lesson  in  dancing  the  minuet,  at 
Edinburgh,  they  found  him  occupied  in  tracing  out 
minutely  with  the  rule  and  compasses,  the  route  gone 
through  by  the  two  dancers,  and  the  different  improve- 
ments of  which  these  figures  seemed  to  him  susceptible. 

Young  borrowed  with  happy  effect,  from  the  sect  of 
the  Friends,  to  which  he  then  belonged,  the  opinion  that 
the  intellectual  faculties  of  children  differ  originally  from 
each  other  much  less  than  is  commonly  supposed.  "  Any 
mnn  can  do  what  any  other  man  has  done,"  became  his 


332  THOMAS    YOUNG. 

favourite  maxim.  And  further,  never  did  he  personally 
himself  recoil  before  trials  of  any  kind  to  which  he 
wished  to  subject  his  system.  The  first  time  he  mounted 
a  horse,  in  company  with  the  grandson  of  Mr.  Barclay, 
the  horseman  who  preceded  them  leapt  a  high  fence. 
Young  wished  to  imitate  him,  but  he  fell  at  ten  paces. 
He  remounted  without  saying  a  word,  made  a  second 
attempt,  was  again  unseated,  but  this  time  was  not 
thrown  further  than  on  to  the  horse's  neck,  to  which  he 
clung.  At  the  third  trial  the  young  learner,  as  his 
favourite  motto  taught,  succeeded  in  executing  what 
another  had  done  before  him.*  This  experiment  need 
not  have  been  i-eferred  to  here,  but  that  it  had  been 
repeated  at  Edinburgh,  and  afterwards  at  Gottingeu,  and 
carried  out  to  a  further  extent  beyond  what  might  seem 
credible.  In  one  of  these  two  cities  Young  soon  after- 
wards entered  into  a  trial  of  skill  with  a  celebrated  rope- 
dancer,  in  the  other,  (and  in  each  case  the  result  of  a 
challenge,)  he  acquired  the  art  of  executing  feats  on 
horseback  with  remarkable  skill,  even  in  the  midst  of 
consummate  artistes,  whose  feats  of  agility  attract  every 
evening  such  numerous  crowds  to  the  circus  of  Franconi. 
Thus,  those  who  are  fond  of  drawing  contrasts  may,  on 
the  one  side,  represent  to  themselves  the  timid  Newton,t 
never  riding  in  a  carriage,  so  much  did  the  fear  of  being 
upset  preoccupy  him,  without  holding  to  both  the  doors 
with  extended  arms,  and,  on  the  other,  his  distinguished 

*  This  anecdote  seems  at  variance  with  what  is  stated  on  the 
authority  of  a  Cambridge  contemporary  of  Young  in  Dr.  Peacock's 
Life,  (p.  119),  that  he  only  once  there  attempted  to  follow  the  hounds, 
Avheii  a  severe  fall  prevented  any  further  exhibitions  of  the  kind. — 
Trcmilator. 

t  This  practice  has  been  described  as  that  of  Newton,  but  the 
motive  assigned  bv  Arago  is  novel. 


YOUNG    AS    A    PHYSICIAN.  333 

rival  galloping  on  the  backs  of  two  horses  with  all  the 
confidence  of  an  equestrian  by  profession. 

In  England,  a  physician,  if  he  does  not  wish  to  lose 
the  confidence  of  the  public,  ought  to  abstain  from  occu- 
pying himself  with  any  scientific  or  literary  research 
which  may  be  thought  foreign  to  the  art  of  curing  dis- 
eases. Young  for  a  long  time  did  homage  to  this  preju- 
dice. His  writings  appeared  under  an  anonymous  veil. 
This  veil,  it  is  true,  was  very  transparent.  Two  con- 
secutive letters  of  a  certain  Latin  motto  served  succes- 
sively in  regular  order  as  the  signature  to  each  memoir. 
But  Young  communicated  the  three  Latin  words  to  all 
his  friends  both  in  his  own  country  and  abroad,  without 
enjoining  secrecy  on  any  one. 

Besides,  who  could  be  ignorant  that  the  distinguished 
author  of  the  theory  of  interferences  was  the  Foreign 
Secretary  of  the  Royal  Society  of  London  ;  that  he  gave, 
in  the  Theatre  of  the  Royal  Institution,  a  course  of  lec- 
tures on  mathematical  physics ;  that,  associated  with 
Sir  H.  Davy,  he  published  a  journal  of  the  sciences, 
&c.  ?  and  moreover,  we  must  say  that  his  anonymous 
disguise  was  not  rigorously  observed  even  in  his  smaller 
memoirs,  and  on  important  occasions,  when,  for  instance, 
in  1807,  the  two  volumes  in  quarto  appeared  of  eight 
hundred  or  nine  hundred  pages  each,  in  which  all 
branches  of  natural  philosophy  were  treated  in  a  manner 
so  new  and  profound,  the  self-love  of  the  author  made 
him  forget  the  interests  of  the  physician,  and  the  name 
of  Young  in  large  letters  replaced  the  two  small  Italics 
whose  series  was  then  terminated,  and  which  would 
have  figured  in  a  rather  ridiculous  manner  in  the  title- 
page  of  this  colo>sal  work. 

Young  had  not  then,  as  a  physician,  either  in  London 


334  THOMAS    YOUNG. 

or  at  Worthing,  where  he  passed  the  sea-bathing  season, 
any  extended  practice.  The  public  found  him,  in  fact, 
too  scientific.  We  must  also  avow  that  his  public  lec- 
tures on  medicine,  those,  for  instance,  which  he  deliv- 
ered at  St.  George's  Hospital,  were  generally  but  ill- 
attended.  It  has  been  said,  to  explain  this,  that  his 
lectures  were  too  dry,  too  full  of  matter,  and  that  they 
were  beyond  the  apprehension  of  ordinary  understandings. 
But  might  not  the  want  of  success  be  rather  ascribed  to 
the  freedom,  not  very  common,  with  which  Young 
pointed  out  the  inextricable  difficulties  which  encounter 
us  at  every  step  in  the  study  of  the  numerous  disorders 
of  our  frail  machine  ? 

Would  any  one  expect  at  Paris,  and  especially  in  an 
age  when  every  one  seeks  to  attain  his  end  quickly  and 
without  labour,  that  a  professor  of  the  faculty  would 
retain  many  auditors  if  he  were  to  commence  with  these 
words,  which  I  borrow  literally  from  Dr.  Young : — 

"  No  study  is  so  complicated  as  that  of  medicine  ;  it 
exceeds  the  limits  of  human  intelligence.  Those  physi- 
cians who  precipitately  go  on  without  trying  to  compre- 
hend what  they  observe,  are  often  just  as  much  advanced 
as  those  who  give  themselves  up  to  generalizations 
hastily  made  on  observations  in  regard  to  which  all 
analogy  is  at  fault."  And  if  the  Professor,  continuing 
in  the  same  style,  should  add,  "  In  the  lottery  of  medi- 
cine the  chances  of  the  possessor  of  ten  tickets  must 
evidently  be  greater  than  those  of  the  possessor  of  five," 
— when  they  believed  themselves  engaged  in  a  lottery, 
would  those  of  his  auditors  whom  the  first  phrase  had 
not  driven  away,  be  at  all  disposed  to  make  any  great 
efforts  to  procure  for  themselves  more  tickets,  or,  to 
explain  the  meaning  of  our  Professor — the  greatest 
amount  of  knowledge  possible  ? 


YOUNG    AS    A    PHYSICIAN.  335 

In  spite  of  his  knowledge,  perhaps  even  from  tlie  very 
cause  that  it  was  so  extensive,  Young  was  totally  want- 
ing in  confidence  at  the  bedside  of  the  patient.  Then 
the  mischievous  effects  which  might  eventually  result 
from  the  action  of  the  medicine  even  the  most  clearly 
called  for  presented  themselves  in  a  mass  to  his  mind ; 
seemed  to  counterbalance  the  favourable  chances  which 
might  attend  the  use  of  them ;  and  thus  threw  him  into 
a  state  of  indecision,  no  doubt  very  natural,  yet  on  which 
the  public  will  always  put  an  unfavourable  construc- 
tion. 

The  same  timidity  showed  itself  in  all  the  works  of 
Young  which  treated  on  medical  subjects.*  This  man, 
so  eminently  remarkable  for  the  boldness  of  his  scientific 
conceptions,  gives  here  no  more  than  a  bare  enumeration 
of  facts.  He  seems  hardly  convinced  of  the  soundness 
of  his  thesis,  either  when  he  attacks  the  celebrated 
Dr.  Eadcliffe,  whose  whole  secret  in  the  most  brilliant 
and  successful  practice  was,  as  he  has  himself  said,  to 
employ  remedies  exactly  the  reverse  of  the  usual  way : 
or  when  he  combats  Dr.  Brown,  who  found  himself,  as 
he  says,  in  the  disagreeable  necessity  of  recognizing,  and 
that  in  accordance  with  the  oflScial  documents  of  an  hos- 
pital attended  by  the  most  eminent  physicians,  that,  on 
the  average,  fevers  left  to  their  natural  course  are  neither 

*  This  timidity  in  medical  speculation  is  entire]}'  borne  out  by  the 
tenor  of  Young's  intellectual  character  as  exhibited  in  such  forcible 
lineaments  in  the  portrait  presented  to  us  by  Dr.  Peacock.  His  mind 
was  essentially  cast  in  a  matter  of  fact  positive,  demonstrative  mould; 
hence  all  subjects  of  abstract  or  doubtful  inquiry,  in  which  probabili- 
ties alone  could  be  estimated,  or  when  the  conclusions  were  to  be  the 
result  of  moral  discrimination,  were  utterly  unsuited  to  him.  His 
medical  character  has  been  viewed,  however,  in  a  much  higher  light 
by  Dr.  Peacocli,  who  has  sought  to  combat  the  unfavourable  impres- 
sions here  advanced.     See  especially  p.  213  and  p.  -^2.— Translator. 


336  THOMAS    YOUNG. 

more  severe  nor  of  longer  duration  than  those  treated  by 
the  best  methods. 

In  1818,  Young,  having  been  named  Secretary  to  the 
Board  of  Longitude,  abandoned  entirely  the  practice  of 
medicine  to  give  himself  up  to  the  close  superintendence 
of  the  celebrated  periodical  work  known  under  the  name 
of  the  Nautical  Almanac.  From  this  date  the  Jo^irnal 
of  the  Royal  Institution  gave  every  quarter  his  numerous 
dissertations  on  the  most  important  problems  of  naviga- 
tion and  asti'onomy.  A  volume  entitled  Illustration  of 
the  Mecanique  Celeste  of  Laplace.,  a  scientific  discussion 
on  the  tides,  amply  attested  that  Young  did  not  consider 
the  employment  he  had  accepted  as  a  sinecure.  This 
employment  became  nevertheless  to  him  a  source  of 
unceasing  disgust.  The  Nautical  Almanac  had  always 
been  from  its  commencement  a  work  exclusively  des- 
tined to  the  service  of  the  navy.  Some  persons  de- 
manded that  it  ought  to  be  made,  besides,  a  complete 
astronomical  ephemeris.  The  Board  of  Longitude, 
whether  right  or  wrong,  not  having  shown  itself  a  strong 
partisan  of  the  projected  change,  found  itself  suddenly 
the  object  of  the  most  violent  attacks.  The  journals  of 
every  party,  AVhig  or  Tory,  took  part  in  the  conflict. 

We  were  no  longer  to  view  it  as  a  union  of  such  men 
as  Davy,  Wollaston,  Young,  Herschel,  Kater,  and  Pond, 
but  an  assembly  of  individuals  (I  quote  the  words),  ''  who 
obeyed  a  Bceotian  influence."  The  Nautical  Almanac, 
hitherto  so  renowned,  was  now  declared  to  have  become 
an  object  of  shame  to  the  English  nation.  If  an  error 
of  the  press  were  discovered,  such  as  there  must  be  in 
any  collection  of  figures  at  all  voluminous,  the  British 
navy,  from  the  smallest  bark  up  to  the  colossal  three- 
decker,  misled  by  an  incorrect  figure,  would  all  together 
be  engulfed  in  the  ocean,  &c. 


NAUTICAL    ALMANAC.  337 

It  lias  been  pretended  that  the  jDrincipal  promoter  of 
these  foolish  exaggerations  did  not  perceive  such  serious 
errors  in  the  Nautical  Almanac  until  after  he  had  un- 
successfully attempted  himself  to  obtain  a  place  in  the 
Board  of  Longitude.     I  know  not  whether  the  fact  was 
so.     In  any  case,  I  would  not  make  myself  the  echo  of 
the  malicious   commentaries   to  which   it  gave  rise ;    I 
ought  not  to  forget,  in  fact,  that  for  many  years  past  that 
member  of  the   Royal  Society  to  whom   I   allude  has 
nobly  devoted  a  part  of  his  large  fortune  to  the  advance- 
ment of  science.     This  commendable  astronomer,  like  all 
men  of  science  whose  thoughts  are  concentrated  on  one 
sole  object,  fell  into  the  error,  which  I  do  not  pretend  to 
excuse,  of  measuring    through    a  magnifying  glass  the 
importance  of  the  projects  lie  had  conceived ;  but  that 
with  which  above  all  he  must  be  reproached  is,  that  he 
did  not  foresee  that  the  hyperbolic  language  of  his  attacks 
would  be  taken  literally ;  that  he  forgot  that  at  all  epochs 
and  in  all  countries  there  are  a  great  number  of  persons 
who  having  nothing  to   console  them  for  their  littleness 
seize,  as  a  prey,  on  all  occasions  of  scandal,  and  under 
the  mask  of  zeal  for  the  public  good  enjoy  the  delio-Jit  of 
being  ignoble  defamers  of  those  of  their  contemporaries 
whose  success  has  been  proclaimed  by  flime.     In  Rome 
he  whose  ofBce  it  was  to  insult  the  triumphant  conqueror 
was  altogether  a  slave  ;  in  Loudon  it  was  a  member  of 
the  House  of  Commons,  from  whom  the  men  of  science 
received  a  cruel   affront.     An   orator  notorious  for  his 
prejudices,  but  who  had  hitherto  vented  his  bitterness 
only  against  productions  of  French  origin,  attacked  the 
most  celebrated  names  in  England,  and  retailed  against 
them   in   open  parliament   puerile    accusations,   with  a 
laughable  gravity.     Ministers  whose  eloquence  was  ex- 

6EC.   SEK.  15 


338  THOMAS    YOUNG. 

ercised  for  hours  on  the  privileges  of  a  rotten  borough, 
did  not  pronounce  a  single  word  in  favour  of  genius. 
The  Board  of  Longitude  was  suppressed  without  oppo- 
sition. The  next  day,  it  is  true,  the  wants  of  an  innu- 
merable marine  service  made  their  imperative  voice 
heard,  and  one  of  the  men  of  science  who  had  been  dis- 
placed, the  former  Secretary  of  the  Board,  Dr.  Young, 
found  himself  recalled  to  his  old  labours.  Paltry  repar- 
ation !  Would  the  man  of  science  feel  less  the  separa- 
tion from  his  illustrious  colleagues, — would  the  man  of 
feeling  less  perceive  that  the  noble  fruits  of  human  intel- 
lect were  subjected  to  tariff  by  the  representatives  of  the 
country,  in  pounds,  shillings,  and  pence,  like  sugar,  pep- 
per, or  cinnamon  ? 

The  health  of  our  colleague,  which  had  already  become 
somewhat  precarious,  declined  from  this  sad  epoch  with 
fearful  rapidity.  Skilful  physicians  by  whom  he  was 
attended  soon  lost  hope.  Young  himself  had  a  con- 
sciousness that  his  end  was  approaching,  and  saw  it 
come  with  an  admirable  calmness.  Until  his  last  hour 
he  occupied  himself  without  intermission  on  an  Egyptian 
dictionary  then  in  the  press,  and  which  was  not  published 
till  after  his  death.  When  his  powers  did  not  permit 
him  any  longer  to  sit  up,  or  to  emi)loy  a  pen,  he  cor- 
rected the  proofs  with  a  pencil.  One  of  the  last  acts  of 
his  life  was  to  exact  the  suppression  of  a  small  publi- 
cation written  with  talent,  by  a  friendly  hand,  and 
directed  against  all  those  who  had  contributed  to  the 
destruction  of  the  Board  of  Longitude.*     Young  died 

*  The  whole  account  of  the  transactions  connected  with  the  abo- 
lition of  the  Board  of  Longitude  must  be  received  with  some  qualifi- 
cation. Arago  writes  on  the  subject  in  his  usual  vehement  tone,  and 
in  the  feeling  in  which  the  whole  affair  would  naturally  be  viewed  by 
a  foreigner,  perhaps  not  intimately  acquainted  with  the  minute  points 


BOARD    OF    LONGITUDE.  339 

suiTouncled  by  a  family  by  whom  he  was  adored,  May 
10,  1829,  barely  at  the  age  of  fifty-six.  Examination 
showed  that  he  suffered  from  ossification  of  the  aorta. 

of  the  case,  and  the  somewhat  different  relative  position  occupied  by 
the  parties  in  England  to  that  in  which  they  might  stand  in  France. 
It  may  be  right  very  briefly  to  point  out  a  few  particulars  in  the  case 
which  are  necessary  for  forming  a  correct  impression  of  it.  The 
Board  of  Longitude,  oi-iginally  instituted,  as  its  name  implied,  for  one 
specific  object,  which  it  was  considered  had  been  sufficiently  attained, 
was  in  1818  remodelled  by  Act  of  Parliament,  when  Dr.  Young  was 
appointed  secretary  to  the  Board  and  superintendent  of  the  Nautical 
Almanac;  the  late  Mr.  F.  Baily,  whose  eminence  in  astronomical 
science  may  perhaps  be  dated  from  that  event,  strongly  pointed  out 
the  numerous  defects  of  the  Nautical  Almanac;  this  led  to  some  con- 
troversy of  rather  a  sharp  nature  between  himself  and  Dr.  Young, 
who  defended  the  existing  system ;  other  astronomers  joined  in  the 
desire  for  these  and  even  more  extensive  improvements,  all  which 
(v/ith  one  slight  concession)  wej'e  steadily  opposed  by  Br.  Young. 
Among  these  advocates  for  reform  were  several  members  of  the  Board 
itself,  who  urged  them  at  its  meetings.  There  was  also  a  very  preva- 
lent impression,  even  among  its  own  members,  that  the  Board  was 
not  well  constituted,  and  might  have  been  capable  of  much  better 
service  to  the  nation  if  its  functions  were  less  restricted  and  the  selec- 
tion of  its  members  placed  on  a  better  footing.  In  other  quarters  im- 
pressions unfavourable  to  its  utility  were  prevalent ;  and  it  can  hardly 
be  matter  of  surprise  that  when  the  Board  was  itself  divided  in  opin- 
ion, the  public  or  the  legislature  should  entertain  doubts  of  its  utility, 
or  even  hostile  feelings  towards  it.  What  were  the  precise  notions  of 
the  government,  or  the  machinations  bj'  which  they  were  influenced, 
it  is  impossible  to  say;  but  it  is  certain  that  in  1828,  chiefly  through 
the  influence  of  5Ir.  Croker,  its  dissolution  was  determined  upon  and 
carried  by  Act  of  Parhament  without  any  opposition  being  attempted. 
Instead,  however,  of  an  enlarged  Board  with  increased  powers,  three 
scientific  advisers  of  the  Admiralty  were  appointed,  of  whom  Dr. 
Young  was  one,  retaining  the  superintendence  of  the  Nautical  Alma- 
nac; a  system  which  has  been  since  remodelled  in  accordance  with 
the  report  of  a  committee  appointed  out  of  the  Astronomical  Society. 
Dr.  Young  appears  all  along  to  have  been  affected  only  by  the  per- 
sonal acrimony  of  some  of  the  attacks  upon  himself  in  relation  to  the 
editorship  of  the  Nautical  Almanac,  and  not  at  all  by  any  feeling  for 
the  Board  of  Longitude,  as  Arago  would  regard  it. 


340  THOMAS    YOUNG. 

I  have  not  dwelt  too  long  on  the  task  imposed,  on  me, 
if  I  have  brought  out,  as  I  wished  to  do,  the  importance 

Thnt  Board,  as  already  observed,  was  divided  against  itself,  and  it 
therefore  fell.  It  was  never  upheld  on  the  only  right  ground.  Neither 
the  Board  nor  the  friends  of  science  sufficiently  urged  the  strong  and 
irresistible  claims  which  they  might  have  preferred  to  the  government 
of  the  country,  that  "  a  council  of  science"  with  extended  powers, 
properly  selected  and  adequately  remunerated,  would  be  the  appro- 
priate adjunct  of  the  government  of  a  coiintry  all  whose  resources  are 
so  powerfully  developed  in  exclusive  dependence  on  the  applications 
of  science. 

The  government  would  thus  have  had  the  means  of  sound  scientific 
advice  constantly  at  hand,  of  which  experience,  proves  they  are  in 
daily  want  on  every  emergency;  and  which  they  obtain  by  asking 
the  gratuitous  services  of  men  of  science,  and  the  crown  would  have 
possessed  the  means  of  making  a  graceful  aclinowledgment  of  the 
services,  and  paying  a  just  tribute  to  the  genius,  of  men  devoted  to 
the  higher  branches  of  the  abstract  sciences,  which  are  of  a  nature 
incapable  in  themselves  of  affording  any  kind  of  remuneration,  or  in 
the  ordinary  course  leading  to  anj'  of  those  honours  or  preferments 
which  await  eminence  in  other  professions. —  Translator. 

The  reader  may  be  referred  for  details  of  the  questions  here  consid- 
ered to  the  following  documents: — 

1.  "  Astronomical  Tables  and  Remarks  for  1822,  published  Decem- 
ber, 1821,"  by  F.  Baily,  Esq.,  with  "Remarks  ou  the  present 
defective  state  of  the  Nautical  Almanac.'''' 

2.  A  Reply  to  these  Remarks  appeared  iu  Mr.  Brande's  Quartei'ly 
Journal  of  Science,  April,  1822.     (Attributed  to  Dr.  Young.) 

3.  Practical  Observations  on  the  Nautical  Almanac,  &c.,  by  Jas. 
South,  F.  R.  S.  1822. 

d.  Reply  to  a  Letter  in  the  Morning  Chronicle  relative  to  the  Gov- 
ernment and  Astronomical  Science,  &c.  by  the  same.     1829. 

5.  Refutation  of  Misstatements,  &c.,  in  a  paper  presented  to  the 
Admiralty  by  Dr.  T.  Young,  and  printed  by  order  of  the  House 
of  Commons,  by  the  same.     1829. 

6.  Further  Remarks  on  the  present  defective  state  of  the  Nautical 
Almanac,  &c.,  by  F.  Baily,  Esq.,  F.  R.  S.,  &c.     1829. 

7.  Report  of  the  Committee  of  the  Astronomical  Society  relative  to 
the  improvement  of  the  Nautical  Almanac,  adopted  by  the  Coun- 
cil of  the  Society  and  approved  and  ordered  to  be  carried  into 
effect  by  the  Lords  Commissioners  of  the  Admiralty,  1830.  Me- 
moirs of  Astronomical  Society,  vol.  iv.  p.  447. 


BOARD    OF    LONGITUDE.  341 

and  novelty  of  the  admirable  law  of  interferences. 
Young  is  now  placed  before  your  eyes  as  one  of  the 
most  illustrious  men  of  science  in  whom  England  may 
justly  take  pride.  Your  thoughts,  anticipating  my  words, 
may  perhaps  perceive  already,  in  the  recital  of  the  just 
honours  shown  to  the  author  of  so  beautiful  a  discovery, 
the  peroration  of  this  historical  notice.  These  anticipa- 
tions, I  regret  to  say,  will  not  be  realized.  The  death 
of  Young  has  in  his  own  country  created  very  Httle  sen- 
sation. The  doors  of  Westminster*  Abbey,  so  easily 
accessible  to  titled  mediocrity,  remained  shut  upon  a  man 
of  genius,  who  was  not  even  a  baronet.  It  was  in  the 
village  of  Farnborough,  in  the  modest  tomb  of  the  family 
of  his  wife,  that  the  remains  of  Thomas  Young  were 
deposited.     The  indifference   of  the  English  nation  for 

8.  A  motion  was  made  in  the  House  of  Commons,  February  23, 
1829,  for  certain  Returns  i-especting  the  Board  of  Longitude  and 
the  Nautical  Almanac,  &c. 
The  Returns  were  made  and  printed  consisting  of  (1)  "A  Memo- 
randum of  a  Statement  made  to  the  Chancellor  of  the  Exchequer 
for  reforming  the  Nautical  Almanac,  and  establishment  of  a  new 
Board  of  Longitude.  (2)  A  Paper  read  at  the  Board,  by  J.  Her- 
schel,  Esq.  (3)  A  Report  on  a  Memorandum,  &c.  by  Thomas 
Young,  M.  D.  In  the  last  Dr.  Young  makes  answer  to  what  he 
considers  objections  raised  in  the  "  Memorandum,"  and  also 
replies  to  those  of  Mr.  Baily  and  Mr.  South.  Sir  J.  South's 
Pamphlet  contains  the  Memorandum, — the  objections  raised  or 
inferred  by  Dr.  Young — his  replies  to  them — all  which  are 
severely  criticized. 
At  p.  60  is  a  curious  account  of  some  discussions  at  Sir  H.  Davy's 

soiree  between  Sir  J.  South  and  Dr.  Young. 
*  The  frequenters  of  Poets'  Corner  need  not  be  reminded  that  lit- 
erature and  science  are  not  excluded  from  their  share  of  funereal 
honours  in  Westminster  Abbe}'.  M.  Arago  here,  as  in  some  other 
passages,  may  naturally  be  a  little  incorrect  in  referring  to  national 
usages.  The  delay  which  occurred  in  regard  to  Young's  monument, 
is  however  not  fully  explained  by  Dean  Peacock.  (See  Life  of 
Young,  p.  485.) — Translator. 


342  THOMAS    YOUNG. 

those  scientific  labours  which  ought  to  add  so  mucli  to 
its  glory,  is  a  rare  anomaly,  of  Avhich  it  would  be  curious 
to  trace  the  causes.  I  should  be  wanting  in  frankness, 
I  should  be  the  panegyrist,  not  the  historian,  if  I  did  not 
avow,  that  in  general  Young  did  not  suificiently  accom- 
modate himself  to  the  capacity  of  his  readers  ;  that  the 
greater  part  of  the  writings  for  which  the  sciences  are 
indebted  to  him,  are  justly  chargeable  with  a  certain 
obscurity.  But  the  neglect  to  which  they  were  long 
consigned  did  not  depend  solely  on  this  cause. 

The  exact  sciences  have  an  advantage  over  the  works 
of  art  or  imagination,  which  has  been  often  pointed  out. 
The  truths  of  which  they  consist  remain  constant  through 
ages  without  suffering  in  any  respect  from  the  caprices  of 
fashion  or  the  decline  of  taste  :  but  thus,  when  once  these 
researclies  rise  into  more  elevated  regions  of  thought, 
on  liow  many  competent  judges  of  their  merits  can  we 
reckon  ?  "When  Richelieu  let  loose  against  the  great 
Corneille  a  crowd  of  that  class  of  men  whom  envy  of  the 
merit  of  others  renders  furious,  the  Parisians  vehemently 
hissed  the  partisans  of  the  despot  Cardinal  and  applauded 
the  poet.  This  reparation  is  denied  to  the  geometer,  the 
astronomer,  or  the  physicist,  who  cultivate  the  highest 
parts  of  science.  Those  who  can  competently  appreciate 
them  throughout  the  whole  extent  of  Europe  never  rise 
above  the  number  of  eight  or  ten.  Imagine  these  unjust, 
indifferent,  or  even  jealous,  (for  I  suppose  that  may  some- 
times be  the  case,)  and  the  public,  reduced  to  believe  on 
hearsay,  would  be  ignorant  that  D'Alembert  had  con- 
nected the  great  phenomenon  of  precession  of  equinoxes 
with  the  principle  of  universal  gravitation  ;  that  Lagrange 
had  arrived  at  the  discovery  of  the  physical  cause  of  the 
libration  of  the  moon  ;  that  since  the  researches  of  La- 


EDINBURGH    REVIEW.  343 

place,  the  acceleration  of  the  motion  of  that  luminary  is 
found  to  be  connected  with  a  i^articular  change  in  the 
form  of  the  earth's  orbit,  &c.  &c.  The  journals  of  science, 
when  thej  are  edited  by  men  of  recognized  merit,  thus 
acquire,  on  certain  subjects,  an  influence  which  some- 
times becomes  fatal.  It  is  thus  I  conceive  that  we  may 
describe  the  influence  which  the  Edinburgh  Review  has 
sometimes  exercised. 

Among  the  contributors  to  that  celebrated  journal  at 
its  commencement,  a  young  writer  was  eminently  distin- 
guished, in  whom  the  discoveries  of  Newton  had  inspired 
an  ardent  admiration.  This  sentiment  so  natural,  so 
legitimate,  unfortunately  led  him  to  misconceive  the  plau- 
sible, ingenious,  and  fertile  character  of  the  doctrine  of 
interferences.  The  author  of  this-  theory  had  not,  per- 
haps, always  taken  care  to  clothe  his  decisions,  his  state- 
ments, his  critiques,  with  those  more  polished  forms  of 
expression  the  claims  of  which  ought  never  to  be  neg- 
lected, and  which  moreover,  became  a  matter  of  imper- 
ative duty  when  the  question  referred  to  the  immortal 
author  of  the  Natural  Philosophy  *   [the   Principia  ?] 

*  It  seems  impossible  to  malce  this  sentence  intelligible  unless  we 
suppose  the  "immortal  author"  spoken  of  to  be  Newton,  and  by  con- 
sequence that  the  title  Nalural  Philosophy  was  a  slip  of  the  writer's 
pen,  for  Principia.  Yet  the  supposition  that  the  hostility  of  the  Eclin- 
burc/h  Review  was  at  all  called  forth  by  any  want  of  courtesy  towards 
Newton  in  the  writings  of  Young  is  wholly  unsupported  by  any  thing 
in  Young's  papers,  in  which  he  cites  the  views  of  Newton  with  the 
greatest  respect. —  Translatm: 

NevHon's  support  of  the  emission  theory  of  light. — The  authority  of 
names  can  never  be  of  any  avail  to  the  truly  inductive  philosopher, — 
his  motto  is  emphatically  "nullius  in  verba."  But  there  has  been 
always  a  propensity  among  writers  on  the  subject  to  dwell  on  such 
authority,  and  to  array  great  names  on  either  side  of  any  of  those  contro- 
verted points  which  have  divided  the  scientific  world.  Perhaps  where 
the  question  is  purely  one  of  opinion  and  refers  simply  to  hypotheses, 


344  THOMAS    YODNG. 

The  penalty  of  retaliation  was  applied  to  him  with  inter- 
est ;  the  Edinhurgh  Revieio  attacked  the  man  of  erudi- 

upheld  for  what  they  are  worth  as  such,  the  weight  of  a  name  may  not 
be  imworthy  of  due  estimation ;  great  experience  and  high  genius  may 
add  value  to  a  pure  Jnjpothcsis  though  it  could  not  to  a  positive  conclu- 
sion. In  regard  to  theories  of  light  this  has  been  conspicuously  exem- 
plified, and  during  a  long  continuance  of  controversial  discussion  it 
has  been  a  matter  of  triumph  to  the  opponents  of  the  undulatory  the- 
ory that  tlie  authority  of  Newton  is  on  their  side.  And  even  Arago 
as  well  as  some  other  supporters  of  it  have  spoken  as  if  regretting  that 
they  were  thus  constrained  to  put  themselves  in  antagonism  to  New- 
ton. They  have  pictured  two  rival  theories,  the  one  headed  by  New- 
ton and  supported  by  Laplace,  Biot,  Brewster  and  Potter,  the  other 
upheld  in  opposition  to  them  bj'  Huyghens,  Hooke,  Euler,  Young, 
Fresnel,  Airy  and  all  the  Cambridge  school. 

But  a  very  slight  inquiry  into  the  real  facts  entirely  dispels  this 
view  of  the  case.  In  particular  Dr.  Young  himself  in  proposing  his 
theory,  so  far  from  opposing  the  Newtonian  views,  expressly  endeav- 
ours to  conciliate  attention  by  claiming  the  weight  of  Newton's  author- 
ity 011  his  own  side :  thus  in  his  paper  "  On  the  Theory  of  Light  and 
Colours,"  (Phil.  Trans.  1801,)  he  commences  by  highly  extolling  the 
optical  researches  of  Newton,  and  then  observes,  "those  who  are 
attached,  as  they  may  be  with  the  greatest  justice,  to 'every  doctrine 
which  is  stamped  with  the  Newtonian  approbation,  will  probably  be 
disposed  to  bestow  on  these  considerations  (i.  e.  his  own  views)  so 
much  the  more  of  their  attention  as  they  shall  appear  to  coincide  more 
nearly  with  Newton's  opinion."  He  then  proceeds  to  examine  in  de- 
tail a  number  of  passages  from  Newton's  writings  in  which  the  theoiy 
of  waves  is  distinctly  upheld  and  even  applied  with  some  precision 
to  the  explanation  of  various  phenomena  of  light,  illustrated  by  their 
analogies  to  those  of  sound. 

It  is  perfectly  true  that  Newton  in  the  actual  investigation  of  several 
phenomena  of  light  adopts  other  hypotheses  than  those  of  waves;  and 
chiefly  the  idea  of  light  (whatever  may  be  its  nature)  being  subject  to 
certain  attractions  and  repulsions, — to  certain  bendings  when  approach- 
ing near  the  edges  of  solid  bodies, — to  certain  peculiar  modifications  or 
changes  in  its  nature  recurring  periodically  at  certain  minute  intervals 
along  the  length  of  a  ray, — to  the  idea  of  a  ray  having  "  sides  "  endued 
with  different  properties ;  in  a  word,  a  variety  of  conceptions,  which  he 
introduces  for  the  purpose  of  giving  some  kind  of  imaginarj'  physical 
representation  of  the  inodiis  operandi  in  each  of  the  several  curious 


ATTACKS    UPON    YOUNG.  345 

tion,  the  writer,  the  geometer,  the  experimenter,  with  a 
vehemence,  with  a  severity  of  expression  almost  with- 


experimental  cases  which  he  had  examined.  In  all  these  there  is  no 
unity  or  community  of  principle,  there  is  at  least  nothing  like  the  spirit 
of  theory,  no  continual  recurrence  to  one  leading  idea, — no  perpetual 
appeal  to  any  one  principle  however  imaginarj',  but  an  attempt  in  each 
isolated  case  to  frame  something  like  an  isolated  hypothesis  to  suit  it, 
and  in  some  way  to  represent  its  phenomena  though  without  any 
attempt  to  connect  them  with  the  others.  It  maj-  perhaps  be  said  that 
all  these  various  suppositions  agree  in  supposing  light  to  be  material, 
to  be  something  emitted  from  the  luminous  source.  But  on  a  closer 
examination  it  seems  far  from  certain  that  even  this  can  be  main- 
tained. The  only  part  of  these  investigations,  perhaps,  in  which  any 
thing  very  positive  of  this  kind  is  distinctly  introduced,  is  when  New- 
ton investigates  tlie  laws  of  refraction,  on  the  express  supposition  of 
small  molecules  attracted  by  the  molecules  of  tlie  medium.  But  in 
this  instance  it  has  been  truly  observed,  that  at  the  time  when  New- 
ton wrote,  no  mathematical  method  existed  by  which  this  kind  of 
action  could  be  reduced  to  calculation  except  those  involving  the  ac- 
tion of  attractive  force.  To  give,  then,  a  mathematical  theory  of  ordi- 
nary reflexion  and  refraction  he  was  necessitated  to  make  use  of  this 
method.  When  he  came  to  investigate  those  more  recondite  phenom- 
ena which  he  (very  appropriately  to  their  apparent  nature)  called 
"inflexion,"  the  idea  most  naturally  and  obviously  presented  was, 
that  some  power  or  influence,  analogous  to  attraction  and  I'epulsion, 
existing  in  the  edge  of  an  opaque  body  to  bend  out  of  their  course  rays 
passing  very  near  it,  and  this  might  seem  to  imply  the  matei'iality  of 
those  rays.  A  kind  of  alternating  action  of  this  sort,  which  he  imag- 
ined necessary  to  account  for  a  part  of  the  effect,  would,  however, 
hardly  be  reconcilable  to  the  idea  of  direct  emission.  It  would  be  a 
difficult  matter  to  conceive  particles  darted  through  space  with  such 
inconceivable  velocity  as  must  belong  to  those  of  light,  and  yet  stop- 
ping to  wave  about,  in  and  out,  as  Newton  expresses  it,  "like  an  eel," 
close  to  the  edge  of  a  body,  by  virtue  of  some  mysterious  influence 
which  it  exercises  upon  them. 

Again:  the  theory  of  those  alternating  states,  conditions,  or  "fits" 
as  he  termed  them,  at  such  minute  intervals  along  the  length  of  ray 
alternately  putting  it  in  a  state  to  be  reflected,  and  again  to  be  trans- 
mitted by  a  transparent  medium,  seem  very  remote  from  the  idea  of  a 
simple  rectilinear  progress  of  molecules  through  space  following  one 
another  at  immense  intervals  of  distance  though  in  inconceivably  rapid 
15* 


346  '  THOMAS    VOUNG. 

out  example  in  scientific  discussion.  The  public  usually 
keeps  on  its  guard  when  such  violent  language  is  ad- 
dressed to  it,  but  in  this  instance  they  adopted  at  the  first 
onset  the  opinions  of  the  journalist  in  which  we  cannot 
fairly  accuse  them  of  inconsiderateness.  The  journalist, 
in  fact,  was  not  one  of  those  unfledged  critics  whose  mis- 
sion is  not  justified  by  any  previous  study  of  the  subject- 
Several  good  papers,  received  by  tlie  Eoyal  Society,  had 
attested  his  mathematical  knowledge,  and  had  assigned 
him  a  distinguished  place  among  the  physicists  to  whom 
optical  science  was  indebted  :  the  profession  of  the  bar  in 
London  had  acknowledged  him  one  of  its  shining  lumi- 
naries ;  the  Whig  section  of  the  House  of  Commons  saw 

succession  in  time.  It  would  be  easy  to  extend  such  remarks ;  but  it 
■will  probably  be  seen,  with  sufficient  evidence  for  our  present  purpose, 
that  neither  in  profession  nor  in  fact,  can  Newton's  name  be  appealed 
to  as  at  all  an  exclusive  supporter  of  the  material  hypothesis  of  light; 
even  if  in  other  passages  he  had  not  distinctly  referred  to  that  of  un- 
dulations. And  of  these  references  a  large  number  are  quoted  from 
different  portions  of  his  writings,  by  Dr.  Young,  in  the  paper  above 
cited.  In  some  of  these,  while  he  admits  the  readiness  with  which  the 
idea  of  waves  represents  the  phenomena,  he  yet  dwells  on  certain  ap- 
parent objections  which  seemed  to  invalidate  that  idea. 

Upon  the  whole  it  appears  that  the  name  of  Newton  can  in  no  way 
be  legitimately  claimed  as  a  partisan  of  either  theory.  Indeed,  it  is 
surprising  that  any  claim  of  the  kind  could  have  been  set  up  as  re- 
gards the  emission  theory  after  his  own  distinct  avowal: — 

"  'Tis  true  that  from  theory  I  argue  the  corporeity  of  light;  but  I  do 
it  without  any  absolute  positiveness,  as  the  word  'perhaps'  intimates; 
and  make  it  at  most  but  a  very  plausible  consequence  of  the  doctrine, 
and  not  a  fundamental  supposition,  nor  so  much  as  any  part  of  it." — 
Phil.  Trans,  vol.  x.  1675,  p.  5086. 

While  in  respect  to  either  hypothesis  it  is  sufficiently  evident  to 
those  acquainted  with  his  writings  that  he  never  systemalically  upheld 
either  the  one  or  the  other;  but  from  time  to  time,  as  each  particular 
investigation  seemed  to  require,  he  adopted  the  one  or  the  other  prin- 
ciple just  as  it  seemed  to  give  the  more  ready  explanation  of  the  point 
before  liim. —  Translator. 


JUSTICE    FINALLY    RENDERED    HIM.  347 

in  him  an  efficient  orator  who  in  parliamentary  struggles 
was  often  the  happy  antagonist  of  Canning  ;  this  was  the 
future  President  of  the  House  of  Peers, — the  present 
Lord  Chancellor.*  How  could  opposition  be  offered  to 
unjust  criticisms  proceeding  from  so  high  a  quarter  ?  I 
am  not  ignorant  what  firmness  some  minds  enjoy  in  the 
consciousness  of  their  being  in  the  right ;  in  the  certainty 
that  sooner  or  later  truth  will  triumph ;  but  I  know  also, 
that  we  shall  act  wisely  in  not  reckoning  too  much  on 
such  exceptions.  Listen,  for  example,  to  Galileo  him- 
self, repeating  in  a  whisper  after  his  abjuration,  "  E  pur 
si  muore  ! "  and  do  not  seek  in  these  immortal  words  an 
augury  for  the  future,  for  they  are  but  the  expression  of 
the  cruel  vexation  which  the  illustrious  old  man  experi- 
enced. Young  also,  in  writing  a  few  pages  which  he 
published  as  an  answer  to  the  Edinburgh  Review,  showed 
himself  deeply  discouraged.  The  vivacity,  the  vehe- 
mence of  his  expressions,  ill  concealed  the  sentiment 
which  oppressed  him.  In  a  word,  let  us  hasten  to  say 
that  justice,  complete  justice,  was  at  length  rendered  to 
the  great  physicist.  After  several  years  the  whole  world 
recognized  in  him  one  of  the  brightest  luminaries  of  the 
age.  It  is  from  France  (and  Young  took  pleasure  in 
himself  proclaiming  it)  that  the  first  sign  of  this  tardy 
reparation  showed  itself.  I  will  add,  that  at  an  epoch 
considerably  before  the  doctrine  of  interferences  had 
made  converts  either  in  England  or  on  the  Continent, 
Young  found  within  his  own  family  circle  one  who  com- 
prehended it,  and  whose  assent  to  it  might  well  console 
him  for  the  neglect  of  the  public.  The  distinguished 
person  whom  I  here  point  out  to  the  notice  of  the  physi- 

*  Lord  Brougham,  who  held  that  office  when  this  biography  was 
written. 


348  THOMAS    TOUNG, 

cists  of  Europe,  will  excuse  me  if  I  complete  this  indis- 
cretion by  stating  the  circumstances. 

In  the  year  1816  I  made  a  tour  in  England  with  my 
scientific  friend  M.  Gay-Lussac.  Fresnel  had  just  then 
entered  on  his  scientific  career  in  the  most  brilliant  man- 
ner, by  the  publication  of  his  memoir  on  Diffi-action. 
This  work  which,  in  our  opinion,  contained  a  capital 
experiment  irreconcilable  with  the  Newtonian  theory  of 
light,  became  naturally  the  first  subject  of  our  discussion 
with  Dr.  Young.  We  were  astonished  at  the  numerous 
qualifications  which  he  put  upon  our  praises  of  it,  until  at 
length  he  stated  to  us  that  the  very  experiment  which  we 
so  much  commended  had  been  published,  so  long  since  as 
1807,  in  his  treatise  on  Natural  Philosophy.  This  asser- 
tion did  not  seem  to  us  well  founded.  It  caused  a  long 
and  minute  discussion.  Mrs.  Young  was  present,  with- 
out appearing  to  take  any  part  in  the  conversation  ;  but 
we  imagined  that  the  weak  fear  of  being  designated  by 
the  ridiculous  sobriquet  of  bas-bleu  rendered  the  ladies 
of  England  very  reserved  in  the  presence  of  foreigners  ; 
and  our  want  of  discernment  did  not  strike  us  till  the 
moment  when  Mrs.  Young  quickly  quitted  her  place  ;  we 
then  began  to  attempt  excuses  to  her  husband,  until  we 
saw  her  reenter  the  room  carrying  under  her  arm  a  large 
quarto  volume.  This  was  the  first  volume  of  the  Natural 
Philosophy.  She  placed  it  on  the  table,  and  without  say- 
ino-  a  word  opened  it  at  page  787,  and  pointed  with  her 
finger  to  a  diagram  in  which  the  curvilinear  route  of  the 
diffracted  bands,  on  which  the  discussion  turned,  was  the- 
oretically established. 

I  trust  I  shall  be  pardoned  these  little  details.  Too 
numerous  examples  may  almost  have  habituated  the  pub- 
lic  to    consider   destitution,    injustice,    persecution,   and 


ENCOURAGEMENT    TO    YOUNG    STUDENTS.  349 

miseiy  as  the  natural  wages  of  those  who  devote  their 
vigils  to  the  development  of  the  human  mind  !  Let  us 
not  then  forget  to  point  out  the  exceptions  whenever  they 
present  themselves.  If  we  wish  that  youth  should  give 
itself  up  with  ardour  to  intellectual  labours,  let  us  show 
them  that  the  glory  attached  to  great  discoveries  allies 
itself,  sometimes  at  least,  with  some  degree  of  tranquillity 
and  happiness.  Let  us  even  withdraw,  if  it  be  possible, 
from  the  history  of  science  so  many  pages  which  tarnish 
its  glory.  Let  us  try  to  persuade  ourselves  that  in  the 
dungeons  of  the  Inquisitors,  a  friendly  voice  had  caused 
Galileo  to  hear  some  of  the  delightful  expressions  which 
posterity  has  kept  sacred  for  his  memory ;  that  behind 
the  thick  walls  of  the  Bastille,  Freret  might  yet  have 
learned  from  the  world  of  science,  the  glorious  rank 
which  it  had  reserved  for  him  among  the  men  of  erudi- 
tion whom  France  honours  ;  that  before  going  to  die  in 
an  hospital,  Borelli  had  found  sometimes  in  the  city  of 
Rome  a  shelter  against  the  inclemency  of  the  atmosphere, 
and  a  little  straw  on  which  to  lay  his  head ;  and  lastly, 
that  the  great  Kepler  had  not  experienced  the  sufferings 
of  hunger. 


350  THOMAS    YOUNG. 


NOTE  BY  THE  AUTHOR. 

The  Journals  having  done  me  the  honour  to  mention  some- 
times the  numerous  testimonies  of  good  will  and  friendship 
which  Lord  Brougham  had  shown  me  in  1834,  as  well  in  Scot- 
land as  in  Paris,  a  word  or  two  of  explanation  here  seem  indis- 
pensable. The  eloge  of  Dr.  Young  was  read  at  a  public  sitting 
of  the  Academy  of  Sciences,  Nov.  26,  1832.  At  this  period 
I  had  never  had  any  personal  acquaintance  with  the  writer  in 
the  Edinburgh  Review,  and  thus  all  charge  of  ingratitude  must 
fall  to  the  ground.  But  could  you  not,  some  might  perhaps 
say,  have  suppressed  entirely,  when  your  paper  was  going  to 
the  press,  all  that  related  to  so  unfortunate  a  controversy  ?  I 
could  have  done  so,  and  in  fact  the  idea  had  occurred  to  me  ; 
but  I  soon  renounced  it.  I  know  too  well  the  elevated  feel- 
ings of  my  illustrious  friend  to  fear  that  he  will  take  offence  at 
my  frankness  in  regard  to  a  question  on  which  I  have  a  pro- 
found conviction  that  the  great  extent  of  his  geni!us  has  not 
preserved  him  from  error.  The  homage  which  I  render  to  the 
noble  character  of  Lord  Brougham  in  now  publishing  this  pas- 
sa>Te  of  the  eloge  of  Young  without  any  modification,  is,  in  my 
mind,  sufficiently  significant  to  render  it  needless  to  add  a  word 
more. 


JAMES     WATT. 


BIOGRAPHY  READ  AT  THE  PUBLIC  MEETING  OF  THE 
ACADEMY  OP  SCIENCES,  ON  THE  8tH  OF  DECEMBER, 
1834. 


Gentlemen, — After  having  waded  through  a  long 
list  of  battles,  assassinations,  plagues,  famines,  catastro- 
phes of  all  sorts  presented  by  the  annals  of  I  know  not 
what  country,  a  philosopher  exclaimed,  "  Happy  the 
nation  whose  history  is  tedious  ! "  Why  ought  we  to 
add,  in  a  literary  point  of  view  at  least,  "  Unhappy  the 
man  on  whom  the  duty  falls  to  relate  the  history  of  a 
happy  people  ! " 

If  the  philosopher's  exclamation  loses  none  of  its  ap- 
positeness  when  applied  to  mere  individuals,  its  counter- 
part characterizes  with  equal  truth  the  position  of  some 
biographers. 

Such  were  the  reflections  that  occurred  to  me,  whilst 
I  was  studying  the  life  of  Jam.es  Watt,  and  collecting 
obliging  communications  from  the  relations,  friends,  and 
companions  of  the  illustrious  mechanic.  His  life,  quite 
patriarchal,  devoted  to  work,  to  study,  and  to  meditation, 
will  not  afford  us  any  of  those  striking  events  the  recital  of 
which,  sprinkled  vv'ith  judgment  among  scientific  details, 
relieves  their  weight.     Still  I   will   relate  it,  if  but   to 


352  JAMES    WATT. 

show  in  what  a  humble  position  tliose  projects  were 
perfected,  that  were  destined  to  raise  the  British  nation 
to  an  unheard-of  degree  of  power.  I  will  especially  en- 
deavour to  characterize,  with  extreme  precision,  the 
fruitful  inventions  which  will  for  ever  connect  the  name 
of  Watt  with  the  steam-engine.  I  foresee  all  the  dan- 
gers of  this  line  of  conduct ;  I  am  aware  that  it  may  be 
said  on  going  out  of  this  room  :  We  expected  an  histor- 
ical eulogy,  but  we  have  only  received  a  dry  and  arid 
lesson.  Besides  this,  the  reproach  would  not  have 
weighed  on  me,  if  the  lesson  had  been  well  understood. 
I  will,  therefore,  exert  every  effort  not  to  tire  your 
patience ;  I  will  keep  in  mind  that  clearness  is  politeness 
in  public  speakers. 

INFANCY  AND  YOUTH  OF  JAMES  VTATT. HIS  AD- 
VANCEMENT TO  THE  APPOINTMENT  OF  ENGINEER 
TO    THE    UNIVERSITY    OF    GLASGOW. 

James  Watt,  one  of  the  eight  Foreign  Associates  of 
the  Academy  of  Sciences,  was  born  at  Greenock,  in 
Scotland,  the  19tli  of  Januaiy,  1736.  Our  neighbours 
on  the  other  side  of  the  Channel,  have  the  good  sense 
to  think  that  the  genealogy  of  a  respectable  and  indus- 
trious family,  is  quite  as  worthy  of  being  preserved  as 
the  parchments  of  certain  titled  families  that  have  be- 
come celebrated  only  by  the  enormity  of  their  crimes 
and  their  vices.  Thus  I  can  say  with  certainty  that  the 
great  grandfather  of  James  Watt  was  an  agriculturist, 
settled  in  the  county  of  Aberdeen  ;  that  he  was  killed 
in  one  of  Montrose's  battles  ;  that  the  conquering  side, 
as  was  customary,  (I  was  going  to  add,  as  is  still  custom- 
ary in  civil  discords,)  did  not  think  death  itself  a  suffi- 
cient expiation  for  tlie  opinions  in   support  of  which  the 


HIS    INFANCY    AND    YOUTH.  353 

poor  farmer  had  fought ;  that  it  punished  the  act  in  the 
person  of  the  son,  by  confiscating  his  property ;  that  the 
unfortunate  child,  Thomas  Watt,  was  received  by  some 
distant  relations  ;  that  in  the  entire  insulation  to  which 
his  difficult  position  condemned  him,  he  assiduously 
devoted  himself  to  deep  studies ;  that  in  more  tranquil 
times,  he  settled  at  Greenock,  where  he  taught  mathe- 
matics and  the  elements  of  navigation  ;  that  he  resided 
at  Crawford's  Dyke,  of  which  borough  he  was  magis- 
trate;  and  that  finally  he  died  in  1734,  at  the  age  of 
eighty-two. 

Thomas  Watt  had  two  sons.  The  eldest,  John,  fol- 
lowed his  father's  profession  at  Glasgow.  He  died  at 
the  age  of  fifty  (1737),  leaving  a  chart  of  the  Clyde,* 
which  was  published  under  the  care  of  his  brother  James. 
This  James,  who  was  the  father  of  the  celebrated  engi- 
neer, and  for  a  long  time  treasurer  of  the  municipal 
council  of  Greenock,  as  well  as  magistrate  of  the  town, 
became  remarkable  in  the  performance  of  his  duties  by 
his  ardent  zeal,  and  an  enlightened  spirit  of  amelioration. 
He  combined,  (do  not  be  alarmed  ;  these  three  syllables, 
that  have  become  a  subject  of  general  anathema  in 
France,  will  not  injure  the  memory  of  James  Watt,)  he 
combined  three  species  of  occupation  ;  he  was  at  once  a 
seller  of  all  sorts  of  nautical  instruments  f  and  stores,  a 

*  This  map  is  reengi'aved  in  the  Memorials  of  Watt,  with  an  adver- 
tisement which  ascribes  its  publication  to  James  Watt,  at  Glasgow 
College;  a  MS.  note  on  one  copy,  said  to  be  in  the  handwriting  of  the 
Great  Engineer,  states  that  it  was  published  by  John  Watt  in  1760. — 
Translator. 

t  It  may  have  been  first  owing  to  an  examination  of  these  instru- 
ments, that  j'oung  Watt,  in  his  eighteenth  year,  in  conformitj-  with 
his  own  desire,  was  apprenticed  to  a  mathematical  instrument-maker 
in  London. —  Translatoi\ 


354  JAMES    WATT. 

builder,  and  a  merchant ;  which  unfortunately,  about  the 
close  of  his  life,  did  not  prevent  certain  comraei'cial  spec- 
ulations from  depriving  him  of  a  portion  of  the  creditable 
fortune  that  he  had  gained  before.  He  died  at  the  age 
of  eighty-four,  in  1782. 

James  Watt,  the  subject  of  this  essay,  was  born  with 
a  very  delicate  constitution.  His  mother,  whose  maiden 
name  was  Muirhead,  gave  him  his  first  instruction  in 
reading.  He  learned  writing  and  ciphering  from  his 
father.  He  also  attended  the  Grammar  School  of  Gree- 
nock ;  and  thus  these  humble  Scotch  seminaries  are 
entitled,  with  just  pride,  to  enroll  the  name  of  this  cele- 
brated engineer  among  the  pupils  that  they  have  formed ; 
as  the  College  of  La  Fleche  boasted  of  Descartes,  as  the 
University  of  Cambridge  still  cites  Newton. 

To  be  correct,  I  must  add  that  frequent  indispositions 
prevented  young  "Watt  from  punctually  attending  the 
public  school  at  Greenock ;  that  during  a  great  portion 
of  the  year  he  was  confined  to  his  room,  and  there 
devoted  himself  to  study,  without  any  out-door  help. 
As  is  frequently  the  case  with  high  intellectual  faculties 
destined  to  yield  great  results,  they  began  to  develop 
tliemselves  in  retirement  and  solitude. 

Watts  was  too  sickly  for  his  parents  to  think  of  urging 
him  to  assiduous  occupation.  They  even  left  his  amuse- 
ments to  his  free  choice.  We  shall  see  whether  he 
abused  this  freedom. 

A  friend  of  Mr.  Watt's  one  day  found  little  James 
lying  on  the  floor,  and  with  a  piece  of  chalk  drawing  all 
sorts  of  intersecting  lines ;  whereupon  he  exclaimed — 
"  Why  do  you  allow  that  child  to  waste  his  time — send 
liim  to  the  public  scliool !  "  Mr.  Watt  answered :  "  You 
might  have  spared  us  this  hasty  judgment ;  before  con- 


ANECDOTE    OF    HIS    YOUTH.  355 

derailing  us,  examine  attentively  what  our  son  is  doing." 
Tlie  apology  soon  followed  ;  the  boy,  only  six  years  old, 
was  seeking  the  solution  of  a  geometrical  problem. 

Prompted  by  an  enlightened  fondness,  the  father  had 
early  furnished  the  young  scholar  with  a  certain  number 
of  tools,  and  he  made  use  of  them  with  great  ability  ;  he 
took  to  pieces  and  put  together  again  all  the  infantine 
toys  that  came  into  his  hands  ;  he  continually  made  new 
ones.  When  older,  he  applied  them  to  the  construction 
of  a  small  electrical  machine ;  the  bright  sparks  from 
which  became  a  lively  subject  of  amusement  and  sur- 
prise to  all  the  playfellows  of  the  poor  invalid. 

Watt,  with  an  excellent  memory,  still  would  not  per- 
haps have  figured  among  the  young  prodigies  of  com- 
mon schools ;  he  would  have  refused  to  learn  lessons 
like  a  parrot,  because  he  felt  an  internal  longing  care- 
fully to  elaborate  the  intellectual  elements  which  they 
presented  to  his  mind.  Nature  had  especially  created 
him  for  meditation.  The  father,  moreover,  augured  very 
favourably  of  the  rising  fltculties  of  his  son.  Other  less 
observant  relations  did  not  participate  in  these  hopes ; 
his  grandmother,  Mrs.  Muirhead,  said  to  him  one  day, — 
"  James,  I  never  saw  such  an  idle  young  man  as  you 
are.  Do  take  a  book,  and  employ  yourself  usefully. 
Upwards  of  half  an  hour  has  elapsed  without  your  say- 
ing a  single  word.  Do  you  know  what  you  have  been 
doing  all  this  time  ?  You  have  taken  off  and  replaced, 
and  taken  off  again,  the  teapot  lid ;  and  you  have  alter- 
nately held  in  the  steam  that  came  out,  first  a  saucer  and 
then  a  spoon ;  you  have  busied  yourself  in  examining 
and  collecting  together  the  little  drops  formed  by  the 
condensation  of  the  steam,  on  the  surface  of  the  china 
and  of  the  silver ;  is  it  not  disgraceful  to  waste  your 
time  in  this  manner  ?  " 


356  JAMES    "WATT. 

In  1750,  each  of  us  in  Mrs.  Muirhead's  position  would 
probably  have  held  the  same  language ;  but  the  world 
has  advanced,  and  general  knowledge  has  advanced  with 
it ;  also,  when  I  shall  have  presently  explained,  that  the 
principal  discovery  of  our  associate  consisted  in  a  special 
manner  of  transforming  steam  into  water,  the  reproaches 
of  Mrs.  Muirhead  will  appear  quite  in  a  different  light ; 
and  little  James  watching  the  tea-pot,  will  be  the  great 
Engineer  anticipating  the  important  discoveries  that  were 
to  immortalize  him ;  every  one  will  then  perceive  how 
remarkable  it  was  that  the  words  condensation  of  steam 
should  so  naturally  have  entered  into  an  account  of 
Watt's  early  childhood.  Independently  of  this,  I  could 
not  but  think,  from  the  singularity  of  the  anecdote,  that 
it  deserved  to  be  preserved.  When  an  opportunity 
offers,  let  us  prove  to  young  people  that  Newton  was 
not  diffident  only  on  that  day  when,  to  satisfy  the  curi- 
osity of  a  high  personage  who  desired  to  know  how 
attraction  had  been  discovered,  he  answered.  By  con- 
stantly thinking  of  it !  Let  us  show  to  everybody,  in 
the  simple  words  of  the  immortal  author  of  the  Prin- 
cipia,  the  real  secret  of  men  of  genius. 

The  love  of  anecdote  that  our  associate  showed  so 
agreeably  during  upwards  of  half  a  century  to  all  those 
around  him,  developed  itself  very  early.  The  proof  will 
be  found  in  some  lines  that  I  am  about  to  quote  and 
translate  from  an  unedited  note  given  in  1798,  by  INIrs. 
Marion  Campbell,  a  cousin  and  juvenile  companion  of 
the  celebrated  engineer.* 

*  I  am  indebted  for  this  curious  documeut  to  my  friend  Mr.  James 
Watt,  of  Soho.  Thanlis  to  the  deep  veneration  that  he  feels  for  the 
memory  of  his  illustrious  father,  and  thanks  to  the  inexliaustible 
complaisance  with  which  he  listened  to  all  my  inquiries,  I  have  been 
able  to  avoid  several  errois  that  have  slipped  into  the  most  esteemed 


ANECDOTE    OF    HIS    YOUTH.  357 

"  During  a  journey  to  Glasgow,  Mrs.  Watt  entrusted 
her  young  son  James  to  one  of  her  friends.  After  a  few- 
weeks  she  returned  to  see  him,  but  most  assuredly  not 
expecting  the  reception  she  met  with.  "  Madam,"  said 
her  friend,  as  soon  as  she  saw  her,  *'  you  must  hasten  to 
take  James  back  to  Greenock.  I  can  no  longer  endure 
the  state  of  excitement  into  which  he  throws  me  ;  I 
am  harrassed  by  want  of  sleep.  Every  night,  when 
the  usual  hour  approaches  for  the  family  to  retire  to 
bed,  your  son  adroitly  contrives  to  raise  a  discussion, 
in  the  course  of  which  he  always  finds  means  to  intro- 
duce a  story  ;  this  story  is  sure  necessarily  to  engender 
a  second,  and  a  third,  &c.  And  these  tales,  whether 
they  be  pathetic  or  comic,  are  so  charming,  so  interest- 
ing, that  the  whole  of  my  family  listen  to  them  with  such 
attention,  that  a  fly  might  be  heard  to  fly.  Thus,  hours 
follow  hours,  without  our  being  aware  of  it ;  but  the  next 
day  I  am  ready  to  drop  with  fatigue.  Dear  madam, 
take  your  son  home." 

James  Watt  had  a  younger  brother,  John,*  who,  by 
deciding  to  follow  his  father's  profession,  left  James  the 
liberty  of  choosing  any  vocation  ;  for  according  to  Scotch 
customs,  it  suffices  if  one  son  adopts  the  paternal  career. 
But  it  was  difficult  to  say  what  vocation  this  would  be, 
for  the  young  student  seemed  to  succeed  equally  well  in 
whatever  he  tried. 

The  shores  of  Loch  Lomond,  already  so  celebrated  by 
the  reminiscences  that  they  affisrd  of  the  historian  Bu- 
chanan, and  of  the  illustrious   inventor  of  Logarithms, 

biographies,  and  from  which  I  myself,  deceived  by  verbal  references 
too  easily  accepted,  should  otherwise  have  fallen  into. 

*  He  was  lost  in  1702,  in  one  of  his  father's  ships,  on  her  passage 
from  Greenock  to  America,  aged  twenty-three  years. 


358  JAMES    WATT. 

developed  liis  taste  for  the  beauties  of  nature  and  for 
botany.  Excursions  to  various  mountains  in  Scotland 
made  bim  feel  that  the  inert  crust  of  the  globe  is  not 
less  w^orthy  of  attention,  and  he  became  a  mineralogist. 
James  availed  himself  also  of  his  frequent  intercourse 
with  the  poor  inhabitants  of  those  picturesque  districts, 
to  learn  their  local  traditions,  their  popular  ballads,  and 
their  ignorant  prejudices.  When  ill  health  confined  him 
to  his  paternal  roof,  chemistry  became  the  principal 
object  of  his  experiments.  Gravesande's  Elements  of 
Natural  History  initiated  him  into  the  thousands  of  won- 
ders in  general  physics  ;  finally,  like  all  invalids,  he 
devoured  all  the  works  on  medicine  and  surgery  that  he 
could  obtain.  These  latter  sciences  had  awakened  such 
a  passion  in  the  student,  that  he  was  detected  one  day 
carrying  into  his  room  the  head  of  a  child  who  had  died 
of  an  unknown  malady,  for  the  purpose  of  dissecting  it. 

Still,  Watt  did  not  decide  either  in  favour  of  botany, 
of  mineralogy,  of  literature,  of  poetry,  of  chemistry,  of 
physics,  or  of  surgery,  although  he  was  so  well  prepared 
for  each  of  those  studies.  In  1755  he  went  to  London 
to  place  himself  under  Mr.  John  Morgan,  a  maker  of 
mathematical  and  nautical  instruments,  in  Finch  Lane, 
Cornhill.  The  man,  who  was  to  cover  England  with 
motive  powers  by  the  side  of  which,  as  to  their  effects  at 
least,  the  old  colossal  machine  of  Marly  would  seem  a 
mere  pygmy, — entered  on  the  manual  art  of  constructing 
with  his  own  hands  subtile,  delicate,  fragile  instruments, 
those  small  but  admirable  reflecting  sextants,  to  which 
nautical  art  owes  its  progress. 

Watt  did  not  remain  above  a  year  at  Mr.  Morgan's, 
and  returned  to  Glasgow,  where  some  heavy  difficulties 
awaited  him.     Attached  to  their  old  privileges,  the  cor- 


VARIOUS    PURSUITS.  359 

porations  of  arts  and  of  trades  regarded  the  young  artist 
from  London  as  an  intruder,  and  obstinately  refused  him 
permission  to  open  even  the  most  humble  workshop. 
Every  means  of  conciliation  failing,  the  University  of 
Glasgow  interfered,  and  ceded  to  young  Watt  a  small 
locality  in  their  own  buildings,  allowing  him  to  open  u 
shop  there  and  honouring  him  moreover  with  the  title  of 
their  Engineer.*  There  still  exist  soine  small  instru- 
ments of  that  epoch,  of  exquisite  workmanship,  made 
entirely  by  Watt's  own  hands.  I  will  add  that  his  son 
has  lately  placed  before  me  the  first  essays  of  a  steam- 
engine,  and  that  they  are  truly  remarkable  by  the  high 
finish  of  the  work,  the  firmness,  the  precision  of  the 
form.  It  was  not  then  without  reason,  whatever  may 
have  been  said  of  it,  that  Watt  spoke  with  complacency 
of  his  own  manual  dexterity. 

Perhaps  you  have  some  reason  to  think,  that  I  carry 
my  scruples  rather  far,  in  claiming  for  our  associate  a 
species  of  merit  which  cannot  add  to  his  glory.  But  I 
will  acknowledge  that  I  never  intend  to  make  a  pedantic 
enumeration  of  the  qualities  with  which  superior  men 
have  been  endowed,  without  recollecting  that  wretched 
general  in  the  age  of  Louis  XIV.  who  always  carried 
one  shoulder  very  high,  because  Prince  Eugene  of  Savoy 
was  rather  deformed,  and  thought  that  this  sufficed  with- 
out his  endeavouring  to  extend  the  likeness  any  farther. 

Watt  had  scarcely  reached  his  one  and  twentieth  year 
when  the  University  of  Glasgow  attached  him  to  their 

*  This  was  not  all.  According  to  Stuart's  Narrative,  Watt  picked 
up  a  practical  acquaintance  with  machines  from  an  industrious  me- 
chanic at  Glasgow;  a  person  "  who  was  by  turns  a  cutler  and  a  white- 
smith, a  repairer  of  fiddles,  a  tuner  of  spinets,  and  a  mender  of  fish- 
ing tackle," — in  a  word,  a  very  useful  man  at  almost  every  thing.— 
Translator. 


360  JAMES    WATT. 

establishment.  He  had  had  as  protectors,  Adam  (Smith, 
author  of  the  celebrated  work  on  The  Wealth  of  Nations  ; 
Black,  whose  discoveries  relative  to  latent  heat  and  car- 
bonate of  lime  must  place  him  in  a  distinguished  rank 
among  the  most  eminent  chemists  of  the  eighteenth  cen- 
tury ;  Robert  Simson,  the  celebrated  restorer  of  the  most 
important  treatises  by  ancient  geometers.  These  great 
men,  however,  thought  at  first  that  they  had  only  deliv- 
ered a  good,  zealous,  and  amiable  workman  from  the 
overbearing  corporations ;  but  they  soon  after  recog- 
nized in  him  a  first-rate  man,  and  bestowed  on  him  their 
warmest  friendship.  The  students  in  the  University 
also  esteemed  it  an  honour  to  be  admitted  into  Watt's 
intimacy.  In  short,  his  shop,  yes,  Gentlemen,  his  shop  ! 
became  a  sort  of  academy,  where  the  illustrious  men  of 
Glasgow  used  to  go  to  discuss  the  most  delicate  questions 
of  art,  of  science,  and  of  literature.  I  would  not  dare,  I 
own,  to  pronounce  what  share  this  young  workman  of 
one  and  twenty  took  in  these  learned  circles,  if  I  could 
not  depend  on  an  unpublished  paper  by  the  most  illus- 
trious of  the  editors  of  the  British  Encyclopedia. 

Robison  says :  "  Although  still  a  student,  I  had  the 
vanity  to  think  myself  suificiently  advanced  in  my 
favourite  subjects,  mechanics  and  physics,  when  I  was 
introduced  to  Watt ;  and  I  will  acknowledge  that  I  was 
not  slightly  mortified  when  I  perceived  how  far  superior 

the  young  workman  was  to  me Whenever  any 

difficulty  arrested  us  in  the  University,  we  used  to  run  to 
our  workman.  When  once  excited,  any  subject  became 
for  him  a  text  for  serious  study  and  discoveries.  He 
never  let  go  his  hold,  until  he  had  entirely  cleared  up 
the  proposed  question  ;  he  either  reduced  it  to  nought,  or 
obtained  from  it  some  net  and  substantial  result 


VARIOUS    PURSUITS.  361 

One  day,  the  desired  solution  seemed  to  require  that 
Leupold's  work  on  INIachines  should  be  read  :  Watt  im- 
mediately learned  German.  On  another  occasion,  and 
for  a  similar  reason,  he  rendered  himself  master  of  the 

Italian  language The  ingenuous  simplicity  of  the 

young  engineer  immediately  procured  for  him  the  good 
will  of  all  who  accosted  him.  Although  I  have  lived 
much  in  the  world,  I  must  assert,  that  it  would  be  impos- 
sible for  me  to  cite  a  second  example  of  so  sincere  and  so 
general  an  attachment  felt  for  a  man  of  uncontested  supe- 
riority. It  is  true  that  this  superiority  was  veiled  by  the 
most  amiable  candour,  and  allied  to  a  firm  resolution  to 
recognize  every  man's  merit  liberally.  Watt  was  even 
inclined  to  assign  things  to  the  inventive  spirit  of  his 
friends  that  were  often  only  his  own  ideas  dressed  up  in 
another  form.  I  have  all  the  more  reason  to  assert  his 
possessing  this  rare  disposition,  because  I  have  myself 
experienced  the  effects  of  it." 

You  will  have  to  decide,  Gentlemen,  whether  it  was 
not  equally  honourable  to  pronounce  these  closing  words, 
as  to  have  inspired  them. 

The  deep  and  varied  studies  to  which  the  circum- 
stances of  his  singular  position  gave  rise,  never  inter- 
fered with  the  young  artist's  professional  work.  He 
attended  to  this  in  the  daytime  ;  and  devoted  the  night 
to  theoretical  researches.  Relying  on  the  resources  of 
his  imagination,  Watt  seemed  to  delight  in  difficult  enter- 
prises, and  those  to  which  he  seemed  least  adapted.  Will 
it  be  believed  that  he  undertook  to  construct  an  organ,  he 
who  was  totally  insensible  to  the  charms  of  music  ;  he 
who  had  never  been  able  even  to  distinguish  one  note 
from  another,  as  g  from  /?  Yet  this  enterprise  was  suc- 
cessfully carried  out.     We  need  scarcely  add,  that  the 


362  JAMES    WATT. 

new  instrument  presented  essential  improvements  in  the 
mechanical  parts,  in  the  regulators,  in  the  method  of 
appreciating  the  power  of  the  wind ;  but  it  will  excite 
astonishment  to  learn  that  its  harmonic  qualities  were 
not  less  remarkable,  and  that  they  charmed  professional 
musicians.  Watt  solved  an  important  part  of  the  prob- 
lem :  he  arrived  at  the  temperament  assigned  by  a  man 
learned  in  the  mystery,  in  aid  of  the  phenomenon  of  the 
vibrations  then  but  ill  understood ;  and  which  he  could 
not  have  dived  into,  but  in  the  profound  though  obscure 
work  of  Dr.  Smith,*  of  Cambi'idge. 

PRINCIPLES    OF    THE    STEAM-ENGINE. 

I  have  now  reached  the  most  brilliant  portion  of  Watt's 
life,  and  also,  I  fear,  the  most  difficult  part  of  my  task. 
The  immense  importance  of  the  inventions  of  which  I  am 
about  to  treat,  cannot  be  doubted  for  one  moment ;  but  I 
may  not  succeed  in  rendering  them  suitably  appreciated, 
without  entering  into  intricate  numerical  comparisons. 
In  order  that  these  comparisons,  if  they  become  essential, 
may  be  easily  seized,  I  will  present  you,  in  the  most  com- 
pact manner  possible,  with  the  delicate  notions  of  physics 
on  which  we  shall  have  to  rest  them. 

By  the  effect  of  simple  changes  of  temperature,  water 
may  exist  in  three  perfectly  different  conditions ;  in  the 
solid  state,  in  the  liquid  state,  and  in  the  aerial  or  gaseous 
state.  Below  zero  on  the  scale  of  the  centigrade  ther- 
mometer, water  becomes  ice  ;  at  100°  it  rapidly  assumes 
the  form  of  gas ;  in  all  the  intermediary  temperatures  it 
remains  fluid. 

*  Dr.  Robert  Smith's  work,  here  aHuded  to,  was  intituled  Eirmonics, 
or  the  Philosophy  of  Musical  Sounds,  and  printed  in  1760.  He  was  also 
the  author  of  the  well-lsnown  System  of  Optics. —  Translator. 


PRINCIPLES    OF    THE    STEAM-ENGINE.  363 

Careful  observation  of  the  instant  of  change  from  one 
of  these  conditions  to  another,  leads  to  discoveries  of  the 
highest  order,  and  which  are  keys  to  the  economical  ap- 
preciations of  steam-engines. 

Water  is  not  necessarily  hotter  than  any  kind  of  ice  ; 
water  may  be  kept  at  the  temperature  of  zero  without 
freezing ;  ice  may  remain  at  zero  without  melting ;  but 
while  this  water  and  this  ice  are  both  of  the  same  tem- 
peratui'e,  are  both  at  zero,  it  seems  difficult  to  believe 
that  they  do  not  differ  but  by  their  physical  properties ; 
that  no  element,  extraneous  to  the  water  so  called,  distin- 
guishes the  solid  water  fi'om  the  fluid.  A  very  simple 
experiment  will  clear  up  this  mystery. 

Mix  a  kilogram  of  water  at  zero  with  a  kilogram  of 
water  at  79°  centigrade  ;  the  two  kilograms  of  the  mix- 
ture will  be  at  a  temperature  of  39°  and  a  half;  that  is 
to  say,  at  the  mean  of  the  two  constituent  fluids.  The 
hot  water  preserves  39°  and  a  half  of  its  former  heat,  and 
has  ceded  39°  and  a  half  to  the  cold  water ;  this  is  very 
natural  and  might  have  been  foreseen. 

But  let  us  repeat  this  experiment  with  one  modifica- 
tion :  instead  of  the  kilogram  of  water  at  zero,  let  us  take 
a  kilogram  of  ice  at  the  same  temperature  of  zero.  From 
the  admixture  of  this  kilogram  of  ice  with  the  kilogram 
of  water  at  79°,  there  will  result  two  kilograms  of  fluid 
water,  because  the  ice  bathed  in  the  hot  water  cannot  fail 
to  melt  and  to  preserve  its  former  weight ;  but  do  not  has- 
tily attribute  to  the  mixture,  as  in  the  preceding  instance, 
a  temperature  of  39°  and  a  half;  for  you  would  be  mis- 
taken ;  the  temperature  will  be  only  zero ;  there  will  be 
no  trace  left  of  the  79°  of  heat  which  the  hot  water 
possessed :  those  79°  disintegrated  the  molecules  of  ice 
they  have  combined  with  them,  but  without  heating  them 
at  all. 


364  JAMES    WATT. 

I  do  not  hesitate  to  represent  this  experiment  of  Black's 
as  one  of  the  most  remarkable  in  modern  physics.  In- 
deed, see  the  consequences  to  which  it  leads. 

Water  at  zero,  and  ice  at  zero,  difi'er  in  their  internal 
constitution.  The  fluid  contains,  beyond  what  the  solid 
body  does,  79°  of  an  imponderable  body  called  caloric. 
Those  79°  are  so  well  hidden  in  the  composition, — I  was 
almost  going  to  say  in  the  aqueous  amalgam,  that  the 
most  sensitive  thermometer  does  not  reveal  their  exist- 
ence. Heat  then,  imperceptible  to  our  senses,  impercep- 
tible to  the  most  delicate  instruments,  latent  heat,  for 
that  is  the  name  given  to  it,  is  one  of  the  constituent  prin- 
ciples of  those  bodies. 

The  comparison  of  boiling  water,  of  water  at  100° 
with  the  vapour  that  rises  from  it,  and  the  temperature 
of  which  is  also  100°,  leads,  though  on  a  much  grander 
scale,  to  analogous  results.  At  the  moment  of  the  forma- 
tion of  steam  of  the  temperature  of  100°,  the  water  at 
the  same  time  imbibes  an  enormous  quantity  of  heat  in  a 
latent  form,  in  a  form  not  sensible  to  the  thermometer. 
When  the  steam  resumes  its  fluid  form,  this  latent  heat  is 
disengaged,  and  heats  all  bodies  it  meets  with  capable  of 
absorbing  it.  If,  for  example,  we  occasion  5-35  kilograms 
of  water  at  zero  to  be  traversed  by  a  single  kilogram  of 
steam  at  100°,  the  steam  will  be  entirely  liquified.  The 
6"35  kilograms  resulting  from  the  mixture  will  be  of  the 
temperature  of  100°.  In  the  composition  of  one  kilogram 
of  steam  then,  a  quantity  of  latent  heat  is  absorbed  that 
would  raise  a  kilogram  of  water,  provided  the  evapora- 
tion was  prevented,  from  zero  to  535°  of  the  centigrade 
scale.  This  result  will  undoubtedly  appear  enormous,  but 
it  is  certain  ;  the  steam  of  water  is  created  only  on  these 
conditions.    Wherever  a  kilogram  of  water  at  100°  evap- 


LATENT    HEAT    IN    STEAM.  365 

orates  naturally  or  artificially,  it  must  appropriate  to  itself, 
in  order  to  be  transformed,  and  it  does  attract  from  the 
surrounding  bodies,  535°  of  heat.  And  these  degrees,  it 
cannot  be  too  often  repeated,  are  integrally  restored  by 
steam  on  whatever  surfaces  it  is  subsequently  liquified. 
This  ingenious  proceeding  is  very  ill  understood,  if  it  is 
supposed  that  the  aqueous  gas  carries  through  the  tubes 
where  it  circulates  only  the  heat  that  is  thermometrically 
sensible :  the  principal  effects  are  due  to  the  constituent 
heat,  the  hidden  heat,  the  latent  heat,  which  disengages 
itself  at  the  moment  when  a  contact  with  cold  surfaces 
restores  the  steam  from  its  gaseous  to  its  fluid  state. 

Henceforward,  then,  we  must  place  heat  among  the 
constituent  principles  of  the  steam  of  water.  Heat  is 
obtained  only  by  burning  wood  or  coal ;  steam  therefore 
has  a  commercial  value  superior  to  that  of  water,  by  all 
the  price  of  the  combustible  used  in  the  act  of  creating 
steam.  If  the  difference  of  the  two  values  is  very  great, 
it  must  be  attributed  to  the  latent  heat ;  for  the  thermo- 
metric  or  sensible  heat  has  but  a  small  share  in  it. 

I  may  perhaps  have  occasion  to  enlarge,  in  the  sequel, 
on  some  other  properties  of  the  steam  of  water.  If  I  do 
not  mention  them  at  this  moment,  it  is  not  that  I  attribute 
to  this  assembly  the  state  of  mind  of  certain  scholars,  who 
said  one  day  to  their  Professor  of  Geometry, — "  Why  do 
you  take  so  much  trouble  to  demonstrate  these  theorems  ? 
We  place  entire  confidence  in  you  ;  give  us  your  ^oord  of 
honour  that  it  is  true,  and  nothing  more  need  be  said  !  " 
But  it  is  my  duty  not  to  abuse  your  patience  ;  I  have  to 
keep  in  mind  also,  that  by  referring  to  special  treatises, 
you  can  easily  fill  up  the  lacunaj  that  I  have  unavoidably 
left. 


366  JAMES    WATT. 


HISTORY  OP  THE  STEAM-ENGINE  IN  ANCIENT  TIMES. 

Let  us  now  endeavour  to  take  the  part  of  those  nations 
and  individuals,  who  appear  to  deserve  to  be  quoted  in 
the  history  of  the  steana-engine.  Let  us  trace  the  chron- 
ological series  of  improvements  made  in  this  machine, 
from  its  first  germs,  which  were  very  ancient,  up  to  the 
discoveries  by  Watt.  I  enter  on  the  subject  with  a  firm 
inclination  to  be  impartial,  with  a  strong  desire  to  render 
to  each  inventor  the  justice  that  is  due  to  him,  with  a 
certainty  of  continuing  a  stranger  to  any  consideration 
unworthy  of  the  mission  that  you  have  given  me,  or  un- 
worthy of  the  majesty  of  science,  or  arising  from  national 
prejudices.  I  acknowledge,  on  the  other  hand,  that  I 
shall  pay  but  little  attention  to  the  numerous  decisions 
already  come  to,  dictated  by  similar  prejudices  ;  that  I 
shall  allow  myself  still  less,  if  possible,  to  be  influenced 
by  the  bitter  criticisms  that  no  doubt  await  me,  for  the 
past  is  a  mirror  of  the  future. 

A  question  well  expressed  is  half  solved.  If  this  sen- 
sible axiom  had  been  attended  to,  the  discussions  relative 
to  the  invention  of  the  steam-engine  would  not  assuredly 
have  presented  the  symptoms  of  acrimony  and  violence 
with  which  they  have  been  impressed  till  now.  But  the 
authors  had  blindly  plunged  into  a  defile  that  had  no 
outlet,  by  wanting  to  find  a  sole  inventor,  in  a  case  that 
requires  us  to  distinguish  several.  The  best  informed 
watchmaker  of  the  history  of  his  art  would  be  struck 
dumb,  if  he  were  asked  in  general  terms,  who  was  the 
inventor  of  watches  ?  Though  the  question  would  not 
embarrass  him  much,  if  it  referred  separately  to  the 
moving  power,  to  the  various  forms  of  escapement,  or  to 
the  balance.     And  so  it  is  with   the  steam-engine  ;    it 


EARLY    USE    OF    STEAM.  867 

now  presents  the  realization  of  several  capital  ideas,  but 
each  quite  distinct,  that  could  not  have  proceeded  from 
one  and  the  same  source,  and  of  which  it  is  our  duty 
cai'efully  to  seek  out  the  origin  and  date. 

If  having  made  any  use  whatever  of  steam,  as  it  has 
been  asserted,  gave  a  right  to  figure  in  its  history,  we 
ought  to  quote  the  Arabs  in  the  first  place ;  because 
from  time  immemorial,  their  principal  food,  the  flour  of 
maize,  which  they  call  couscoussoii,*  has  been  cooked 
by  steam  in  cullenders  placed  over  rustic  boilers.  Such 
an  instance  suffices  to  show  up  the  ludicrous  natui'e  of 
the  principle  whence  it  results. 

•  Our  countryman  Gerbert,  the  same  who  wore  the 
tiara  as  Sylvester  II.,  does  he  acquire  more  real  claims 
when,  about  the  middle  of  the  ninth  century,  he  made 
the  tubes  of  an  organ  in  the  Cathedral  of  Rheims  resound 
by  means  of  steam  from  water  ?  I  think  not ;  in  the 
embryo  Pope's  instruments  I  perceive  a  current  of  steam 
substituted  for  a  current  of  common  air,  to  produce  the 
usual  musical  phenomenon  from  the  organ  pipes  ;  but  by 
no  means  a  mechanical  effect,  properly  so  called. 

The  first  example  of  motion  generated  by  steam  is  to 
be  found  in  a  toy  still  older  than  Crcrbert's  organ  ;  in  an 
eolipyle  by  Hero  of  Alexandria,  the  date  of  which  is  as 
far  back  as  120  B.  c.     Perhaps  it  may  be  difficult,  not 

*  This  kiiskus,  or  cuscasou,  is  a  very  nutritious  dish;  it  consists  of 
com  paste  crumbled  and  put  into  an  earthen  cullender  over  a  boiling 
pot  in  which  meat  or  fowls,  with  ochra  (pisum  ochrus)  and  other  vege- 
tables, are  stewing;  and  which  is  luted  or  stopped  close  round  the 
junction.  The  contents  of  the  cullender  are  therefore  dressed  by 
steam.  How  ancient  this  mode  of  cooking  may  be  we  know  not,  but 
the  Arabs  only  go  back  to  the  flight  in  a.d.  622;  about  which  time, 
as  tradition  has  it,  it  was  invented  by  Mahomet  when  his  health 
required  wholesome  and  savoury  food.—  Translator. 


368  JAJIES    WATT. 

possessing  aviy  figure,  to  give  a  clear  idea  of  the  mode  of 
action  in  this  little  apparatus  ;  still  I  will  attempt  it. 

When  gas  escapes  in  a  certain  direction  from  the  vase 
in  ■which  it  is  contained,  this  vase  by  means  of  reaction 
will  be  inclined  to  move  in  a  diametrically  opposite 
direction.  The  recoil  of  a  gun  loaded  with  gunpowder 
is  a  similar  agency ;  the  gas  engendered  by  the  combus- 
tion of  the  saltpetre,  the  charcoal,  and  the  sulphur,  rushes 
into  the  air  according  to  the  direction  of  the  gun ;  the 
reaction,  produced  in  the  rear,  reaches  the  shoulder  of 
the  person  who  fires  it ;  it  is  on  the  shoulder  then  that 
the  recoil  must  act.  To  change  the  direction  of  the 
recoil,  it  would  sutHce  to  make  the  jet  of  gas  issue  in 
another  direction.  If  the  gun  were  closed  at  the  end, 
and  were  pierced  only  by  a  lateral  opening  horizontally 
perpendicular  to  its  dii'ection,  the  gas  from  the  powder 
would  escape  laterally  and  horizontally ;  therefore  the 
recoil  would  act  perpendicularly  to  the  direction  of  the 
gun  ;  and  its  force  would  be  exerted  on  the  arms  and 
not  on  the  shoulder.  In  the  former  instance,  the  recoil 
pushed  the  man  who  fired  from  the  front  to  the  rear,  as 
if  to  upset  him  ;  in  the  second  instance  it  would  tend  to 
turn  him  round  on  his  own  axis.  Let  the  gun  then  be 
invariably  fixed,  and  horizontally,  to  a  vertical  movable 
axis,  and  at  the  instant,  of  being  fired,  it  will  alter  its 
direction  more  or  less,  and  it  will  also  make  the  axis  turn. 

Continuing  the  same  arrangements,  let  us  suppose  the 
rotatory  vertical  axis  to  be  hollow,  but  closed  at  its  upper 
end ;  let  it  rise  from  the  base  as  a  sort  of  cliimney  trom 
the  caldron  where  gas  is  engendered ;  let  there  be 
besides  a  free  lateral  communication  between  the  inte- 
rior of  tiiis  axis  and  the  interior  of  the  gun's  barrel,  so 
that,  after  having  filled  the  interior  of  the  axis,  the  steam 


EARLY    USE    OF    STEAM.  369 

enters  the  gun  barrel,  and  issues  by  the  lateral  horizontal 
opening.  Except  as  to  intensity,  this  steam  in  escaping 
will  act  like  the  gases  disengaged  from  the  powder  in  the 
barrel  of  the  gun  when  closed  at  the  end,  and  pierced 
laterally ;  only,  we  should  not  have  but  a  mere  shock 
as  occurred  in  the  instance  of  the  sudden  and  harsh 
explosion  from  the  gun  ;  on  the  contrary,  the  rotatory 
motion  will  be  uniform  and  continuous,  like  the  cause 
which  engenders  it. 

Instead  of  only  one  gun,  or  rather  instead  of  merely 
one  horizontal  tube,  let  several  be  adapted  to  the  ver- 
tical rotatory  tube,  and  we  shall  have,  with  the  exception 
of  some  slight  differences,  the  ingenious  apparatus  of 
Hero  of  Alexandria. 

Here  we  should,  doubtless,  have  a  machine  in  which 
the  steam  of  water  creates  motion,  and  may  produce 
mechanical  effects  of  some  importance  ;  it  would  be 
truly  a  steam-engine.  But  let  us  hasten  to  add  that  it 
would  have  no  real  point  of  contact,  either  in  its  shape, 
or  the  moving  power's  mode  of  action,  with  the  machines 
of  that  kind  now  in  use.  If  ever  the  reaction  of  a  cur- 
rent of  steam  becomes  practically  useful,  we  must,  with- 
out hesitation,  refer  the  idea  back  to  Hero ;  though  at 
present  the  rotatory  eolipyle  can  only  be  quoted  here  as 
carving  on  wood  is  cited  in  the  history  of  printing.* 

*  These  reflections  are  applicable  also  to  the  project  that  Branca, 
an  Italian  architect,  published  at  Rome,  in  1629,  in  a  work  entitled 
Le  Macliine,  and  which  consisted  in  generating  a  rotatory  movement 
by  directing  the  steam  issuing  out  of  an  eolipyle  as  breathings,  or  in 
a  current,  or  on  the  pallets  of  a  wheel.  If,  contrary  to  all  probability, 
steam  is  some  day  usefully  employed  in  the  simple  form  of  blowing, 
Branca,  or  the  author,  now  unknown,  from  whom  he  may  have  bor- 
rowed the  idea,  will  take  the  first  rank  in  the  history  of  this  new 
species  of  machines.  Relative  to  the  machines  of  the  present  day,  the 
claims  of  Branca  would  be  quite  null. 
16* 


370  JAMES    WATT. 

HISTORY    OF    THE    STEAM-ENGINE    IN    KECENT    TIMES. 

In  our  manufacturing  machines,  in  our  packet-boats, 
in  our  railways,  the  motion  results  directly  from  the 
elasticity  of  steam.  It  is  therefore  of  importance  to  seek 
where  and  how  the  idea  of  this  power  first  arose. 

Neither  the  Greeks  nor  the  Romans  were  ignorant 
that  the  steam  of  water  can  acquire  a  prodigious  me- 
chanical power.  They  already  explained,  by  the  aid  of 
the  sudden  evaporation  of  a  certain  quantity  of  this 
fluid,  the  frightful  earthquakes  which  in  a  few  seconds 
hurl  the  ocean  beyond  its  natural  limits  ;  which  over- 
turned from  their  very  foundations  the  most  solid  monu- 
ments of  human  labour  ;  which  suddenly  create  danger- 
ous rocks  in  the  midst  of  deep  seas  ;  and  which  heave 
up  high  mountains  in  the  very  centre  of  continents. 

Whatever  may  be  said  of  it,  this  theory  of  earthquakes 
does  not  show  that  its  authors  had  devoted  themselves  to 
appreciations,  to  experiments,  to  exact  measurements. 
No  one  now  ignores  that  at  the  moment  when  the  incan- 
descent metal  flows  into  the  founder's  moulds  of  earth 
or  plaster,  a  few  drops  of  any  fluid  contained  in  them 
would  suffice  to  occasion  dangerous  exi)losions.  Not- 
withstanding the  progress  of  science,  modern  founders 
do  not  always  avoid  such  accidents  ;  how  then  could  the 
ancients  entirely  keep  clear  of  them  ?  Whilst  they  cast 
thousands  of  statues,  splendid  ornaments  of  their  temples, 
of  their  public  places,  of  their  gardens,  of  the  private 
dwellings  of  Athens  and  of  Rome,  misi'ortunes  must  have 
occurred;  the  artisans  discovered  the  immediate  cause.; 
the  philosophers,  on  the  other  hand,  following  out  the 
spirit  of  generalization,  which  was  the  characteristic  of 
their  schools,  saw  in  them  miniatures,  or  true  images,  of 
Etna's  eruptions. 


KARLY    USE    OF    STEAM.  371 

All  this  may  be  true,  without  having  the  least  impor- 
tance in  the  history  that  now  occupies  us.  I  have  not 
even  insisted,  I  aeknowledge,  so  much  on  these  slight 
lineaments  of  ancient  science  relative  to  the  power  of 
steam,  but  in  order  to  live  at  peace,  if  possible,  with  the 
Daciers  of  both  sexes,  with  the  Dutens  of  our  own 
epoch.* 

Both  natural  and  artificial  powers,  before  becoming 
really  subservient  to  the  use  of  man,  have  almost  always 
been  adopted  for  objects  of  superstition.  Nor  will  the 
steam  of  water  be  an  exception  to  the  general  rule. 

The  chronicles  informed  us  that  on  the  banks  of  the 
Weser,  the  god  of  the  ancient  Teutones  sometimes  indi- 
cated his  displeasure  to  them  by  a  sort  of  thunder-clap, 
which  was  immediately  followed  by  a  cloud  that  filled 
the  sacred  area.  The  image  of  their  god  Busterich, 
found,  it  is  said,  in  some  excavations,  clearly  reveals  the 
way  in  which  the  pretended  prodigy  was  obtained. 

The  statue  was  of  metal.  The  hollow  head  contained 
an  amphora  of  water.  Wooden  plugs  closed  the  mouth 
and  a  hole  above  the  forehead.  Some  charcoal,  adroitly 
placed  in   the  cavity  of  the  cranium,  gradually  warmed 

*  For  the  same  reason,  I  cannot  dispense  with  here  relating  an 
anecdote,  which,  notwithstanding  its  romantic  style,  and  containing 
what  we  now  know  to  be  contrary  to  the  way  in  which  steam  acts, 
still  shows  the  high  opinion  that  the  ancients  had  formed  of  this  me- 
chanical agent.  It  is  related  that  Anthemins,  Justinian's  architect, 
occupied  a  house  next  door  to  that  of  Zeno,  and  to  annoy  that  ora- 
tor, who  was  his  declared  enemy,  he  placed  in  the  ground  floor  of  his 
own  house  several  cauldrons  containing  water;  that  from  an  opening 
made  in  the  lid  of  each  of  these  there  proceeded  a  flexible  tube,  which 
was  conducted  into  the  party-wall  and  up  to  the  beams  that  supported 
the  floors  in  Zeno's  house;  in  short,  that  those  floors  heaved  as  if 
there  had  been  a  violent  earthquake,  as  soon  as  fire  was  applied  to 
the  boilers. 


372  JAMES    WATT. 

the  fluid.  Soon  the  steam  that  was  generated  made  the 
tompions  fly  out  with  a  great  report ;  then  it  escaped 
in  two  violent  jets,  and  formed  a  thick  cloud  between  the 
god  and  his  stupefied  worshippers.  It  would  appear 
that  in  the  middle  ages  some  monks  thought  the  inven- 
tion a  good  prize,  and  that  the  head  of  Busterich  has  not 
acted  before  assembled  Teutones  only.* 

In  order  to  meet  with  useful  notions  on  the  properties 
of  steam,  after  the  first  glimpses  given  by  the  Greek 
philosophers,  we  are  obliged  to  pass  over  an  interval  of 
twenty  centuries.  It  is  true  that  then  some  precise,  con- 
clusive, and  irresistible  experiments  follow  upon  conjec- 
tures devoid  of  pi'oofs. 

In  1605,  Flurence  Rivault,  gentleman  of  the  bed-cham- 
ber to  Henry  IV.,  and  preceptor  to  Louis  XIII.,  discovers, 
for  example,  that  a  shell  or  bomb,  if  made  thick  and  con- 
taining water,  when  placed  on  the  fire  after  being  well 
closed,  (so  as  to  prevent  the  steam  from  expanding  freely 
in  the  air  in  proportion  as  it  is  generated,  will  sooner  or 
later  explode.  The  power  of  steam  is  here  found  char- 
acterized by  a  clear  and,  to  a  certain  degree,  sensitive 
proof,  with  numerical  appreciations ;  but  it  is  still  pre- 
sented to  us  as  a  terrible  means  of  destruction.! 

*  Hero  of  Alexandria  attributed  the  sounds,  the  objects  of  so  much 
controversy,  issuing  from  the  statue  of  Memnon  wlien  the  rays  of  the 
rising  sun  shone  upon  it,  to  the  passage,  through  certain  openings,  of 
a  current  of  steam  that  the  solar  heat  was  deemed  to  have  produced 
at  the  expense  of  the  fluid  with  which  the  Egyptian  priests,  it  is  said, 
provided  the  interior  of  the  pedestal  of  the  Colossus.  Solomon  de 
Cans,  Kircher,  &c.,  have  gone  so  far  as  to  wish  to  discover  the  spe- 
cial arrangements  by  which  the  theocratic  fraud  took  possession  of 
credulous  imaginations;  but  all  these  suppositious  lead  us  to  think 
that  they  have  not  guessed  right,  even  if  there  be,  in  this  respect,  any 
thing  to  guess. 

t  If  any  learned  man  were  to  think  that  by  stopping  at  Flurence 


VARIOUS    INVENTORS.  873 

Some  eminent  minds  did  not  stop  short  at  this  meagre 
reflection.  They  conceived  that  mechanical  forces,  as 
well  as  human  passions,  must  become  useful  or  injurious, 
according  as  they  are  well  or  ill  directed.  In  the  special 
instance  of  steam,  the  simplest  arrangement  suffices  to 
adapt  this  redoubtable  elastic  power  to  productive  labour ; 
which,  according  to  all  appearances,  shakes  the  earth  from 
its  very  foundations,  which  surrounds  the  furnace  of  the 
statuary  with  real  dangers,  and  which  shatters  the  thick- 
est bomb  into  a  hundred  fragments  ! 

In  what  state  does  this  projectile  exist  before  its  ex- 
plosion ?  The  lower  part  contains  some  very  hot  water, 
but  still  fluid  ;  the  rest  of  the  cavity  is  filled  with  steam. 
This  steam,  it  being  the  characteristic  trait  of  all  gaseous 
substances,  exerts  its  action  equally  in  every  direction : 
it  presses  with  similar  intensity  on  the  water  and  on  the 
metallic  envelope  that  contains  it.  Let  us  apply  a  tap  to 
the  lower  part  of  the  bomb.  As  soon  as  it  is  open,  the 
water,  being  urged  by  the  steam,  will  rush  out  with  ex- 
treme swiftness.  If  the  tap  opens  into  a  tube,  which, 
after  curving  round  the  exterior  of  the  shell,  rises  up  ver- 
tically, the  water,  being  forced  to  change  its  course,  will 
rise  up  in  the  tube  in  proportion  to  the  elasticity  of  the 
steam  ;  or,  for  it  is  the  same  thing  though  in  other  words, 

Rivault  I  have  not  p;one  back  far  enough;  if  he  were  to  borrow  a  quo- 
tation from  Alberti,  who  wrote  in  1411 ;  if,  according  to  tliat  author, 
he  were  to  tell  us  that  from  the  beginning  of  the  fifteenth  century,  the 
lime-burners  feared  much  for  themselves  and  their  kilns,  from  the  ex- 
plosion of  pieces  of  limestone  fortuitously  containing  some  cavities,  I 
should  answer  that  Alberti  himself  was  ignorant  of  the  real  cause  of 
those  terrible  explosions,  for  he  attributed  them  to  the  air  in  the  small 
cavities  being  transformed  into  steam  by  the  action  of  flame.  I  must 
remark,  in  conclusion,  that  a  piece  of  limestone,  accidentally  hollow, 
would  not  have  afforded  the  means  of  numerical  appreciation  of  which 
Rivanlt's  experiment  seems  susceptible. 


374  JAMES    WATT. 

the  water  will  rise  in  proportion  to  its  temperature.  The 
only  limits  of  the  ascending  movement  will  be  the  resist- 
ance of  the  walls  of  the  apparatus. 

For  our  bomb  let  us  substitute  a  thick  metal  caldron, 
of  vast  capacity,  and  nothing  will  prevent  our  carrying 
large  quantities  of  fluid  to  indefinite  heights  by  the  sim- 
ple action  of  steam  ;  we  shall  have  constructed,  in  the  full 
meaning  of  the  word,  a  steam-engine  capable  of  emptying 
or  exhausting. 

You  now  know  the  invention  which  France  and  Eng- 
land have  disputed  upon,  as  formerly  seven  towns  of 
Greece  claimed  respectively  the  honour  of  having  been 
the  cradle  of  Homer.  On  the  other  side  of  the  Chan- 
nel the  honour  is  assigned  to  the  Marquis  of  Worcester, 
of  the  illustrious  house  of  Somerset.  On  this  side  of  the 
Straits,  we  feel  that  it  belongs  to  a  humble  engineer,* 
almost  entirely  forgotten  in  biographical  works  ;  to  Solo- 
mon de  Cans,  born  at  Dieppe,  or  in  its  environs.  Let  us 
cast  an  impartial  glance  on  the  claims  of  these  two  com- 
petitors. 

Worcester,  deeply  implicated  in  the  political  intrigues 
of  the  latter  years  of  the  i-eigns  of  the  Stuarts,  was  con- 
fined in  the  tower  of  London. 

"  Que  faire  en  p.areil  gite,  a  moins  que  I'on  ne  songe?  " 
What  could  we  do  in  such  a  bed  but  dream? 

*  The  term  "un  humble  ing^nieur"  is  hardly  applicable,  for  De 
Caus  was,  before  the  year  1612,  engineer  and  architect  to  Louis  XIII., 
King  of  France;  he  then  entered  the  service  of  t!ie  Elector  Palatine, 
who  married  the  daughter  of  James  I.,  with  whom  he  came  to  Eng- 
land, and  was  employed  by  the  Prince  of  Wales  in  ornamenting  Eich- 
mond  Gardens.  His  work  was  entitled  Les  Raisons  des  Forces  Mou- 
vcmtes,  nvec  cUverses;  Mnchines  tant  utiles  que  plnisantes.  In  Partington's 
Lectures  on  the  Steam  Engine,  he  quotes  a  book  by  Isaac  De  Caus, 
"natif  de  Dieppe;"  it  is  named  Nouvelle  Invention  de  lever  V  Eau  plus 
hant  que  sa  source,  avec  quelques  Machines  movmintes  par  le  nioyen  de 
fEau;  it  is  a  folio  volume  without  date  or  place. —  Translator. 


REASON    OF    MOVING    FORCES.  375 

Now  one  day,  according;  to  tradition,  the  lid  of  the 
saucepan,  in  which  his  dinner  Avas  being  cooked,  suddenly 
rose.  Worcester  then  considered  the  strangeness  of  the 
phenomenon  that  he  had  just  witnessed.  The  thought 
now  occnri-ed  to  him  that  the  same  power  which  had 
raised  the  lid  might  become,  under  certain  circumstances, 
a  useful  and  convenient  motive  power.  After  recovering 
liis  liberty,  he  described,  in  1663,  in  a  book  entitled  Cen- 
tury of  Inventions*  the  means  by  which  he  intended  to 
realize  his  idea.  The  essential  part  of  these  means,  as 
far  at  least  as  they  can  be  understood,  is  the  bomb  half 
filled  with  a  fluid,  and  the  vertically  ascending  tube,  as 
we  just  now  described. 

This  bomb,  this  same  tube,  are  drawn  in  the  Reason 
of  Moving  Forces,  a  work  by  Solomon  de  Caus.  There, 
the  idea  is  presented  clearly,  simply,  and  without  any 
pretension.  Its  origin  has  nothing  romantic  in  it ;  it  is 
not  connected  with  the  events  of  civil  war,  nor  with  a 
celebrated  state  prison,  nor  even  with  the  rising  of  the 
lid  of  a  prisoner's  saucepan ;  but,  what  is  of  intinitely 
more  importance  in  a  question  of  priority,  it  is,  by  its 
publication,  forty-eight  years  older  than  the  Century  of 
Inventions,  and  foi'ty-one  years  anterior  to  Worcester's 
imprisonment. 

Thus  reduced  to  a  comparison  of  dates,  the  debate 
seemed  to  be  brought  to  a  close.  Indeed,  how  maintain 
that  1615  had  not  preceded  1663?  But  those  persons 
whose  principal  aim  was  to  expel  any  French  name  from 
this  important  chapter  of  the  history  of  the  sciences,  im- 
mediately changed   their  ground,  as   soon   as   they  had 

*  It  is  expressly  stated  on  the  title-page  of  this  pamphlet,  that  it 
was  written  in  the  year  1655,  though  not  published  till  imZ.— Trans- 
lator. 


376  JAMES    WATT. 

occasioned  the  Reasons  of  Moving  Forces  to  be  disin- 
terred from  tlieir  dusty  shelves.  Without  hesitation  tliey 
pulled  down  their  former  idol ;  the  Marquis  of  Worcester 
was  sacrificed  to  the  desire  of  annulling  the  claims  of 
Solomon  de  Cans  ;  the  bomb  placed  on  a  burning  brazier 
with  its  ascending  tube,  ceased  at  last  to  be  the  true  germ 
of  the  present  steam-engine  !  * 

As  to  myself,  I  do  not  grant  that  the  man  was  of  no 
utility  who,  reflecting  on  the  enormous  elasticity  of  steam 
when  greatly  heated,  was  the  first  to  perceive  that  it 
might  be  used  to  raise  great  quantities  of  water  to  all 
imaginable  heights.  I  cannot  admit  that  no  mention  is 
due  of  the  engineer  who  was  also  the  first  to  describe  a 
machine  adapted  to  realizing  such  effects.  Let  us  not 
forget  that  we  cannot  judge  soundly  of  the  merit  of  an 
invention,  without  transferring  ourselves  in  imagination 
to  the  epoch  in  which  it  was  made ;  without  expelling 
from  our  mind  for  the  time  all  the  knowledge  that  subse- 
quent centuries  have  poured  in  upon  us.  Let  us  imagine 
an  ancient  mechanic,  Archimedes,  for  example,  consulted 
on  the  means  of  raising  the  water  contained  in  a  vast, 
closed,  metallic  recipient,  to  a  great  height.  He  would 
certainly  speak  of  great  levers,  of  single  or  multiplied 
pulleys,  of  a  windlass,  perhaps  of  his  ingenious  screw  ; 
but  what  would  be  his  surprise  if  to  solve  the  problem 
some  one  would  be  content  with  a  fagot  and  a  match  ? 

*  In  Les  Raisons  des  Forces  Mouvantes,  it  is  evident  that  De  Caus 
ascribes  tlie  force  wliicli  shivered  tlie  shell  entirely  to  the  air;  and  he 
seems  to  consider  that  tlie  force  of  the  air  proceeded  from  the  water 
which  exhaled  in  it.  M.  Arago  cannot  be  borne  out  in  saying,  of  those 
who  do  not  arrive  at  his  conclusions,  that  "d'dcarier  tout  nom  Fran- 
gais"  was  their  principal  thought.  We  know  not  to  whom  he  alludes 
in  assigning  such  a  base  motive,  but  the  assertion  infringes  greatly  on 
the  impartiality  which  he  promised  us. —  Translator. 


REASON    OF    MOVING    FORCES.  377 

"Well,  I  must  ask,  should  we  dare  to  refuse  the  epithet  of 
invention  to  a  proceeding  at  which  the  immortal  author 
of  the  earliest  and  true  principles  of  statics  and  hydro- 
statics would  have  been  astonished  ?  The  apparatus  of 
Solomon  de  Caus,  that  metallic  envelop  in  which  an 
almost  indefinite  motive  power  is  created  by  the  aid  of  a 
fagot  and  a  match,  will  always  figure  nobly  in  the  his- 
tory of  the  steam-engine.* 

It  is  very  doubtful  Avhethcr  Solomon  de  Caus,  or  Wor- 
cester ever  had  their  apparatus  made.  This  honour  be- 
longs to  an  Englishman,!  to  Captain  Savery.J    I  compare 

*  It  has  been  printed  that  G.  B.  Porta  had  given  in  his  Spiritali,  in 
1606,  nine  or  ten  years  before  the  publication  of  Solomon  de  Caus's 
work,  the  description  of  a  machine  intended  to  raise  water  by  means 
of  the  elastic  power  of  steam.  I  have  elsewhere  shown  that  the  learned 
Keapolitan  does  not  spenl;  either  directly  or  indirectly,  of  a  machine  in 
the  passage  alluded  to ;  that  his  aim,  that  his  only  aim,  was  to  deter- 
mine experimentally  the  relative  volumes  of  water  and  of  steam;  that 
in  the  small  physical  apparatus  employed  for  this  purpose,  according 
to  the  very  words  of  the  author,  the  steam  could  not  raise  the  water 
more  than  a  few  centimetres  (some  inches);  that  in  the  whole  descrip- 
tion of  the  experiment,  there  is  not  a  single  word  implying  the  idea 
that  Porta  knew  the  power  of  this  agent,  and  the  possibility  of  apply- 
ing it  to  the  production  of  a  ujeful  machine. 

Is  it  thought  that  I  ought  to  have  quoted  Porta,  at  least  on  account 
of  his  researches  on  the  transformation  of  water  into  steam?  But  I 
should  then  say  that  the  phenomenon  had  already  been  studied  with 
attention  by  Professor  Besson  of  Orleans,  about  the  middle  of  the  six- 
teenth century,  and  that  one  of  the  treatises  of  that  mechanic  in  1569, 
contains  a  special  essay  on  determining  the  relative  volumes  of  water 
and  steam. 

t  Bonnain  says  that,  after  Kircher's  death,  a  model  was  found  in  his 
museum  of  a  machine  which  tliat  enthusiastic  writer  had  described  in 
1656,  and  which  differed  from  that  of  Solomon  de  Caus  only  in  one  re- 
spect— the  motive  steam  was  engendered  in  a  vessel  totally  distinct 
from  that  containing  the  water  to  be  elevated. 

I  Thomas  Savery  was  a  sailor,  but,  not  being  in  the  Royal  Navy,  is 
styled  Esquire  Savery  in  the  Royal  Society  correspondence.  Nor  is 
our  author  quite  right  in  supposing  this  was  the  first  engine.     Tlie 


378  JAMES    WATT. 

the  machine  constructed  by  that  engineer  in  1698,  to  that 
of  his  predecessors,  although  he  introduced  some  essential 
modifications  into  it ;  that,  amongst  others,  of  generating 
the  steam  in  a  separate  vessel.  Although  it  may  signify- 
little  relative  to  principle  whether  the  steam  be  generated 
from  the  same  water  that  is  to  be  elevated  and  in  the 
same  caldron  where  it  is  to  act,  or  from  a  separate  vessel 
to  be  admitted  at  will  through  a  tube  of  communication 
furnished  with  a  tap  above  the  fluid  that  is  to  be  expelled, 
it  is  not  so  in  practice.  Another  alteration,  still  more 
useful  and  worthy  of  special  mention,  equally  due  to  Sa- 
very,  will  be  more  appropriately  treated  of  in  the  article 
that  we  shall  devote  in  the  sequel  to  the  labours  of  Papin 
and  Newcomen. 

Savery  had  entitled  his  work  The  Miner's  Friend. 
But  the  miners  did  not  show  themselves  sensible  of 
his  politeness.  With  only  one  exception,  none  of  them 
ordered  his  machine.  They  have  been  used  only  to  dis- 
tribute water  through  various  parts  of  palaces  and  coun- 
try houses,  parks  and  gardens ;  recourse  has  been  had  to 
them  only  to  overcome  a  difference  of  levels  of  twelve  or 
fifteen  metres.  We  must  keep-  in  mind,  however,  that 
the  danger  of  explosion  would  have  been  very  great,  if 
the  immense  power  had  been  given  to  this  apparatus 
that  the  inventor  asserted  they  could  bear. 

Marquis  of  Worcester  did  actually  make  au  "apparatus"  to  drive 
water  up  by  fire ;  aud  Cosmo  de  Medici,  Grand  Duke  of  Tuscauy,  de- 
scribes in  his  Biai-y  that  he  saw  it  in  operation  at  Vauxhall,  in  the 
year  1C56, — "  went  beyond  the  palace  of  the  Archbishop  of  Cauter- 
bury,  to  see  au  hydraulic  machine  invented  by  my  Lord  Somerset, 
Marquis  of  Worcester.  It  raises  water  more  than  forty  geometrical 
feet  by  the  power  of  one  man  only ;  and  in  a  very  short  space  of  time 
will  draw  up  four  vessels  of  water  through  a  tube  or  channel  not  more 
than  a  span  in  width."  Savery's  engine  was  an  improvement  upon 
this  by  the  introduction  of  a  vacuum. —  Translator. 


MODERN    STEAM-ENGINE.  379 

Notwithstanding  the  incompleteness  of  Savary's  prac- 
tical success,  this  engineer's  name  deserves  to  hold  a  very 
distinguished  place  in  the  history  of  the  steam-engine. 
Those  persons  whose  life  has  been  devoted  to  speculative 
exertions,  are  little  aware  of  the  distance  there  is  between 
the  pi'oject,  apparently  the  most  studied,  and  its  reali- 
zation. Not  that  I  presume  to  say,  with  a  celebrated 
German  Professor,  that  Nature  always  exclaims  no,  no  ! 
when  we  wish  to  raise  a  corner  of  the  veil  with  which  she 
covers  herself;  but,  in  following  up  the  same  metaphor, 
it  may  be  permitted  to  assert  that  the  enterprise  increases 
in  difficulty,  in  delicacy,  and  in  uncertainty,  in  proportion 
as  it  requires  the  united  efforts  of  moi'c  artists,  and  the 
employment  of  more  matei-ial  elements  ;  in  these  various 
respects,  and  considering  the  nature  of  the  epoch,  no  one 
can  have  felt  himself  more  unfavourably  situated  than 
Savery. 

MODERN  STEAM-ENGINE. 

I  have  spoken  hitherto  of  steam-engines,  the  resem- 
blance of  which  to  those  that  now  bear  that  name  may 
be  more  or  less  contested.  We  shall  now  treat  of  the 
modern  steam-engine,  of  that  which  is  in  use  in  our  man- 
ufactories, in  our  boats,  at  the  entrance  of  nearly  all  our 
wells  and  mines.  We  shall  see  it  created,  then  enlarge 
and  develop  itself,  sometimes  by  the  inspiration  of  clever 
men,  sometimes  by  the  prickings  of  necessity,  for  neces- 
sity is  the  mother  of  genius. 

The  first  name  that  we  shall  meet  in  this  new  period 
is  that  of  Denis  Papin.  It  is  to  Papin  that  France  will 
owe  the  honourable  rank  that  she  may  claim  in  the  his- 
tory of  the  steam-engine.  Still  the  highly  legitimate 
pride,  which  these  successes  inspire  us  with,  will  not  be 
unmixed.     We  shall  find  the  claims  of  our  countrymen 


380  JAMKS    WATT. 

nowhere  but  in  foi'eign  collections  ;  his  principal  works 
will  be  published  beyond  the  Rhine  ;  his  liberty  will  be 
menaced  by  the  revocation  of  the  edict  of  Nantes  ;  it  Avill 
be  in  a  painful  exile  that  he  will  temporarily  enjoy  that 
privilege  of  which  studious  men  are  most  jealous,  tran- 
quillity of  mind.  Let  us  hasten  to  throw  a  veil  over  the 
deplorable  results  of  our  civil  discords  ;  let  us  forget  that 
fanaticism  was  attached  to  the  religious  opinions  of  the 
physicist  of  Blois  and  return  to  mechanics ;  in  this  re- 
spect at  least  the  orthodoxy  of  Papin  has  never  been 
disputed. 

There  are  two  things  to  be  considered  in  every  ma- 
chine ;  on  one  hand  the  moving  power,  on  the  other  the 
arrangement,  inore  or  less  complicated,  of  the  fixed  and 
movable  parts,  and  by  the  aid  of  which  the  moving 
power  transmits  its  action  to  the  resistance.  At  the 
height  to  which  mechanical  knowledge  has  now  attained, 
the  success  of  a  machine  intended  to  produce  great  effects, 
depends  chiefly  on  the  moving  power,  on  the  way  of  ap- 
plying it,  and  economizing  its  action.  And  therefore  it 
was  to  produce  an  economical  moving  power  capable  of 
making  the  piston  of  a  large  cylinder  oscillate  constantly, 
that  Papin  devoted  his  life.  Then  to  obtain  from  the 
oscillations  of  the  piston  the  power  required  to  turn  the 
stones  of  a  corn  mill,  the  cylinders  of  a  flatting  mill,  the 
paddle-wheels  of  a  steamboat,  the  bobbins  of  a  spinning 
mill :  to  raise  the  heavy  hammer  that  strikes  with  re- 
doubled blows  enormous  masses  of  incandescent  iron,  on 
its  coming  out  of  the  reverberating  furnace :  to  cut  thick 
bars  of  metal  with  the  two  jaws  of  the  shears,  as  we  cut 
ribbon  with  sharp  scissors :  those  are,  I  repeat  it,  so  many 
problems  of  a  very  secondary  order,  and  that  would  not 
puzzle  the  commonest  engineers.     We  may  employ  our- 


ATMOSPHERIC    ENGINES.  381 

selves,  therefore,  exclusively  with  the  means  by  the  aid 
of  which  Papin  proposed  to  induce  his  oscillating  motion. 

Let  us  imagine  a  large  vertical  cylinder,  open  at  top, 
and  its  base  resting  on  a  metallic  table,  pierced  with  a 
hole  that  a  cock  can  either  close  or  open  at  will. 

Introduce  a  piston  into  this  cylinder,  that  is  to  say,  a 
circular  plate,  filling  it  entirely  but  movable,  that  shall 
exactly  close  it.  The  atmosphere  will  rest  with  all  its 
weight  on  the  upper  surface  of  this  species  of  diaphragm, 
and  will  push  it  from  the  top  to  the  bottom.  The  portion 
of  atmosphere  that  occupies  the  lower  part  of  the  cylin- 
der will  tend,  by  reaction,  to  produce  an  inverse  move- 
ment. This  second  force  will  be  equal  to  the  first  if  the 
tap  is  open,  because  gas  presses  equally  in  all  directions. 
The  piston  will  thus  find  itself  urged  by  two  opposite 
forces,  which  will  equalize  each  other.  It  will  descend, 
however,  though  only  by  reason  of  its  gravity.  A  coun- 
terpoise, slightly  heavier  than  the  piston,  will  suffice  to 
raise  it,  on  the  contrary,  up  to  the  summit  of  the  cylin- 
der, and  keep  it  there.  Suppose  the  piston  to  have 
reached  this  extreme  position.  Let  us  seek  the  means  to 
make  it  descend  from  thence  with  great  force,  and  carry 
it  up  again. 

Let  us  imagine  after  having  shut  the  lower  cock,  we 
succeed  in  suddenly  annihilating  all  the  air  contained  in 
the  cylinder, — in  a  word,  to  render  it  a  vacuum.  A 
vacuum  once  made,  the  piston  not  receiving  any  pressure 
but  from  the  external  atmosphere  which  presses  it  from 
above,  will  descend  rapidly.  On  this  movement  being 
.achieved,  the  cock  will  be  opened.  The  air  will  thereby 
return  underneath  to  counterbalance  the  upper  atmos- 
phere. As  at  the  beginning,  the  counterpoise  will  make 
the  piston  remount  to  the  cylinder,  and  all  the  various 


382  JAMES    WATT. 

parts  of  the  aj^paratus  will  be  found  in  their  initial  state. 
A  second  evacuation,  or,  if  we  like  it  better,  a  second 
annihilation  of  the  internal  air,  will  again  make  the 
piston  fall,  and  so  on. 

The  true  moving  power  in  this  arrangement  would  be 
the  weight  of  the  atmosphere.  Let  us  hasten  to  unde- 
ceive those  who  would  think  that  they  found  in  the  facility 
with  which  we  walk,  and  even  run  through  the  air,  an 
index  of  the  weakness  of  this  motive  power.  With  a 
cylinder  of  two  metres  in  diameter,  the  effort  made  by 
the  piston  of  the  pump  in  descending,  the  weight  that  it 
could  raise  to  an  equal  height  with  the  cylinder  at  each 
of  these  oscillations,  would  be  35,000  kilograms.  This 
enormous  power,  frequently  renewed,  may  be  obtained 
by  a  very  simple  apparatus,  if  we  discover  a  prompt 
and  economical  method  of  alternately  generating  and 
destroying  the  atmospheric  pressure  at  will,  in  a  metal 
cylinder. 

This  problem  was  solved  by  Papin.  Its  beautiful  and 
great  solution  consists  in  substituting  an  atmosphere  of 
steam  for  the  common  atmosphere ;  by  replacing  the 
latter  with  a  gas  which  at  100  centigrade  degrees  has 
exactly  the  same  elastic  force,  but  with  the  important 
advantage,  not  possessed  by  the  atmosphere,  that  the 
power  of  aqueous  gas  is  very  soon  destroyed  on  its 
temperature  being  lowered,  that  it  ends  by  almost  en- 
tirely disappearing  if  sufficiently  cooled.  I  should  equally 
well  characterize  Papin's  discovery,  and  in  few  words,  if 
I  said,  that  he  proposed  to  use  the  steam  of  water  to  make 
a  vacuum  in  large  spaces ;  and  that  this  is  besides  a  prompt 
and  economical  method.* 

*  An  English  engineer,  deceived  no  doubt  by  some  imperfect  trans- 
lation, asserted  not  long  since  that  the  idea  of  employing  the  steam  of 


PAPIN  S    MODEL    ENGINES.  383 

The  machine  in  which  our  countryman  was  the  first  to 
combine  the  elastic  force  of  steam  with  the  property  pos- 
sessed by  this  vapour  of  annihilating  itself  by  cooling,  he 
never  made  on  a  large  scale.  His  experiments  were 
always  made  with  simple  models.  The  water  intended 
to  generate  the  steam  was  not  even  contained  in  a  separ- 
ate vessel ;  enclosed  in  the  cylinder,  it  rested  on  the 
metal  plate  that  closed  the  orifice  at  the  bottom.  It  was 
this  plate  that  Papin  heated  directly,  to  transform  the 
water  into  steam ;  it  was  from  the  same  plate  that  he 
took  away  the  fire  when  he  wished  for  condensation  to 
be  effected.  Such  a  proceeding,  barely  allowable  in  an 
experiment  intended  to  verify  the  correctness  of  a  prin- 
ciple, would  evidently  be  still  less  admissible  if  the  piston 
were  required  to  move  with  some  celerity.  Papin,  whilst 
saying  that  success  might  be  attained  "  by  various  con- 
structions easy  to  imagine,"  does  not  indicate  any  of  them. 
He  leaves  to  his  successors  both  the  merit  of  applying 
his  fruitful  idea,  and  that  of  inventing  the  details,  which 
alone  could  ensure  the  success  of  the  machine. 

In  our  early  researches  respecting  the  employment  of 
steam,  we  have  had  to  quote — ancient  philosophers  of 
Greece  and  Rome  ;  one  of  the  most  celebrated  mechanics 
of  the  Alexandrian  school ;  a  pope  ;  a  gentleman  of  the 
court  of  Henri  IV. ;  a  hydraulist,  born  in  Normandy  (in 
that  province  fruitful  in  great  men,  that  has  enriched 
the  national  Pleiad  with  Malherbe,  Corneille,  Poussin, 
Fontenelle,  Laplace,  and  Fresnel)  ;    a  member  of  the 

water  in  one  find  the  same  machine,  as  an  elastic  power  and  as  a  rapid 
means  of  forming  a  vacuum,  belonged  to  Hero.  On  my  side  I  have 
proved,  unanswerably,  that  the  Alexandrian  mechanic  had  never 
thought  of  steam;  that  in  his  apparatus  the  alternate  movement  was 
to  result  only  from  the  dilatation  and  the  condensation  of  air,  arising 
from  the  intermittent  action  of  the  solar  rays. 


384  JAMES    WATT. 

House  of  Lords ;  an  English  engineer ;  finally,  a  French 
doctor,  of  the  Royal  Society  of  London ;  *  for,  we  must 
acknowledge  it,  Papin,  almost  always  exiled,  was  only  a 
correspondent  of  our  Academy.  Now,  however,  simple 
artisans,  mere  workmen,  will  enter  the  list.  All  classes 
of  society  will  thus  have  concurred  towards  the  crea- 
tion of  a  machine  by  which  the  whole  world  was  to 
benefit. 

In  1705,  fifteen  years  after  the  publication  of  Papin's 
first  memoir  in  the  Acts  of  Leipzig,  Newcomen  and 
Cawley,  one  of  them  a  hardware  man,  the  other  a  gla- 
zier at  Dartmouth,  in  Devonshire,  constructed  (be  pleased 
to  observe  that  I  did  not  say  projected,  for  the  difference 
is  great),  constructed  a  machine  intended  to  effect  drain- 
age, and  in  which  there  was  a  separate  caldron  for  gener- 
ating the  steam.  This  machine,  as  well  as  Papin's  small 
model,  has  a  vertical  metal  cylinder,  closed  at  the  bottom, 
open  at  the  top,  with  a  well-adjusted  piston,  intended  to 
travel  from  end  to  end,  both  rising  and  falling.  Both  in 
the  one  apparatus  and  in  the  other,  when  the  steam  can 
freely  reach  the  base  of  the  cylinder,  fill  it,  and  thus 
counterbalance  the  pressure  of  the  external  atmosphere, 
the  ascending  movement  of  the  piston  is  effected  by  a 

*  The  ingenious  Dr.  Denis  Papin  was  intimately  connected  with 
the  Eoyal  Society  and  its  illustrious  president,  Newton,  since  he  held 
the  office  of  curator  to  that  body,  on  a  salary  of  forty  pounds  per 
annum.  It  is  to  be  regretted'  that  the  funds  of  the  Societj',  then,  were 
so  low  that  some  of  Papin's  offered  experiments  seem  to  have  hung 
fire,  on  account  of  the  expenses  amounting  to  fifteen  pounds !  Newton 
reported  favourably  on  the  proposal;  and  Papin  said,  "I  am  fully  per- 
suaded that  Esquire  Savery  is  so  well-minded  for  the  public  good  that 
he  will  desire,  as  much  as  anybody,  that  this  may  be  done."  It  is  a 
singular  incident  in  the  history  of  the  wonderful  engine,  that  though 
Papin  invented  the  safety-valve,  he  did  not  apply  it  to  his  steam-ma- 
chine.—  Translator. 


MODE    OF    REFRIGERATING.  385 

counterpoise.  In  the  English  machine,  in  short,  in  imi- 
tation of  Papin's,  as  soon  as  the  piston  has  reached  its 
maximum  of  ascent,  the  steam  that  had  tended  to  push  it 
there  is  refrigerated  ;  thus  a  vacuum  is  created  through- 
out the  space  that  the  piston  had  traversed,  and  the  ex- 
ternal atmosphere  forces  it  to  descend  again. 

To  obtain  the  requisite  refrigeration,  we  already  know 
that  Papin  contented  himself  with  removing  the  chafing- 
dish  that  heated  the  base  of  the  little  metallic  cylinder. 
Newcomen  and  Cawley  had  recourse  to  an  arrangement 
far  preferable  in  every  respect :  they  poured  an  ample 
quantity  of  cold  water  into  the  circular  space  contained 
between  the  outer  surface  of  the  cylinder  of  their  ma- 
chine and  the  internal  surface  of  a  second  rather  larger 
cylinder,  which  served  as  an  envelop  to  the  first.  The 
cold  was  gradually  communicated  through  all  the  thick- 
ness of  the  metal,  and  lastly  reached  the  steam  itself.* 

Papin's  machine,  thus  perfected  as  to  the  manner  of 
cooling  or  condensing  the  steam,  excited  the  proprietors 
of  mines  to  the  highest  pitch.  It  spread  rapidly  through 
several  counties  of  England,  and  rendered  great  service. 
The  slowness  of  its  movements,  the  necessary  conse- 
quence of  the  tardiness  with  which  the  steam  cooled  and 
lost  its  elasticity,  was  still  a  subject  of  great  regret. 
Chance  fortunately  indicated  a  very  simple  way  of  obvi- 
ating this  impediment. 

At  the  beginning  of  the  eighteenth  century  the  art  of 
casting   metallic  cylinders,  and  of  hermetically  sealing 

*  Savery  had  already  adopted  throwing  cold  water  on  the  exterior 
surface  of  a  metal  vase,  to  condense  the  steam  within  it.  This  was 
the  origin  of  his  partnership  with  Newcomen  and  Cawley ;  yet  we 
must  not  forget  that  Savery' s  patent,  his  machines,  and  the  work  in 
which  he  describes  them,  are  posterior  by  several  years  to  Papin's 
memoirs. 

SEC.    SER.  17 


386  JAJIES    WATT. 

them  by  means  of  movable  pistons,  was  still  in  its  in- 
fancy. Wherefore  in  Newcomen's  early  engines,  the 
piston  was  covered  with  water  intended  to  fill  up  the 
vacancies  between  the  circumference  of  this  movable 
piece  and  the  surface  of  the  cylinder.  To  the  great  sur- 
prise of  the  manufacturers,  one  of  their  engines  began 
one  day  to  oscillate  much  faster  than  usual.  After  many 
examinations  it  was  ascertained  that  on  that  day  the  pis- 
ton was  pierced,  that  some  cold  water  fell  into  the  cylinder 
by  little  drops,  and  that  by  passing  through  the  steam, 
they  annihilated  it  rapidly.  From  this  fortuitous  inci- 
dent may  be  dated  the  entire  abandonment  of  all  exterior 
refrigeration,  and  the  adoption  of  a  watering  pot,  to  shed 
a  shotver  of  cold  water  throughout  the  capacity  of  the 
cylinder  at  the  instant  of  the  piston's  descent.  The 
alternate  up  and  down  motion  now  acquired  all  the  de- 
sired swiftness. 

But  let  us  see  whether  there  was  not  another  equally 
important  improvement  effected  also  by  chance. 

Newcomen's  first  engine  required  the  most  uninter- 
rupted attention  from  the  pei'son  who  had  to  open  and 
shut  the  cocks  either  to  introduce  the  steam  into  the 
cylinder,  or  to  throw  in  the  cold  shower  intended  to  con- 
dense it.  It  happened  on  a  certain  day  that  this  person 
was  young  Henry  Potter.*  The  companions  of  this 
child  were  then  at  play,  and  their  exclamations  of  joy 
tantalize  him  severely.  He  longs  to  go  and  join  them  ; 
but  the  task  entrusted  to  him  would  not  allow  of  half  a 
minute's  absence.  His  mind  becomes  excited ;  strong 
passion  awakes  his  genius  :  he  discovers  relative  con- 
nections of  which  he  had  never  dreamt  before.     Of  the 

*  The  name  of  this  play-loving  and  ingenious  boy  appears  to  have 
been  Humjjhrey  Potter. —  Translator. 


WATKK    AND    STEAM    COMPARED.  387 

two  taps,  the  one  was  to  be  opened  at  the  moment  when 
the  beam,  that  Newcomen  had  been  the  first  to  introduce 
to  such  good  purpose  in  his  engines,  had  completed  the 
descending  oscillation,  and  it  must  be  shut  exactly  at  the 
opposite  oscillation.  The  management  of  the  second  tap 
must  be  the  exact  contrary.  The  positions  of  the  balance 
and  of  the  taps  are  necessarily  dependent  on  each  other. 
Potter  seizes  on  this  fact :  he  perceives  tliat  the  beam 
may  impress  on  the  other  pieces  all  the  motion  that  the 
play  of  the  engine  required,  and  instantly  realizes  his 
conception.  Several  cords  are  fastened  to  the  handles  of 
the  taps  ;  the  opposite  ends  Potter  ties  to  portions  of  the 
beam  suitably  selected  ;  thus  the  purchase  which  this  ex- 
ercises on  certain  cords  while  rising,  and  those  that  it 
exercises  on  others  in  descending,  supplant  the  manual 
efforts  ;  for  the  first  time  the  engine  works  by  itself;  for 
the  first  time  no  other  workman  is  seen  near  it  but  the 
stoker,  who  from  time  to  time  goes  to  keep  up  the  fire 
under  the  boiler. 

For  the  cords  of  young  Potter,  the  constructors  soon 
substituted  rigid  vertical  rods  fixed  to  the  beam  and  fur- 
nished with  several  pegs  which  pressed  the  heads  of  the 
several  taps  or  valves  either  downwards  or  upwards. 
The  rods  themselves  have  been  exchanged  for  other 
combinations ;  but  however  humiliating  such  an  acknowl- 
edgment may  be,  all  these  inventions  are  mere  modifica- 
tions of  the  mechanism  suggested  to  a  child  by  the  wish 
to  join  his  httle  companions  at  play. 

watt's  labours  in  the  steam-engine. 
In  physical  cabinets  we  find  a  good  many  machines  on 
which  industry  had  founded  great  hopes,  though  the  ex- 
pense of  their  manufacture,  or  that  of  keeping  them  at 


388  JAMES    WATT. 

work,  has  reduced  them  to  be  mere  instruments  of  demon- 
stration. This  would  have  been  the  final  fate  of  New- 
comen's  machine,  in  localities  at  least  not  rich  in  combus- 
tibles, if  Watt's  efforts,  of  which  I  must  now  present  you 
with  an  analysis,  had  not  come  in  to  give  it  an  unhoped- 
for deo-ree  of  perfection.  This  perfection  must  not  be 
considered  as  the  result  of  some  fortuitous  observation,  or 
of  a  single  inspiration  of  genius  ;  the  inventor  achieved  it 
by  assiduous  labour,  by  experiments  of  extreme  delicacy 
and  correctness.  One  would  say  that  Watt  had  adopted 
as  his  guide  that  celebrated  maxim  of  Bacon's — "  To 
write,  speak,  meditate,  or  act,  when  we  are  not  sufficiently 
provided  with/aci!s  to  stake  out  our  thoughts,  is  like  navi- 
gating without  a  pilot  along  a  coast  strewed  with  dangers, 
or  rushing  out  on  the  immense  ocean  without  compass  or 
rudder." 

In  the  collection  belonging  to  the  University  of  Glas- 
gow, there  was  a  Httle  model  of  a  steam-engine  by  New- 
comen  that  had  never  worked  well.  The  Professor  of 
Physics,  Anderson,  desired  Watt  to  repair  it.  In  the 
hands  of  this  poweri'ul  workman  the  defects  of  its  con- 
struction disappeared  ;  from  that  time  the  apparatus  was 
made  to  work  annually  under  the  inspection  of  the  aston- 
ished students.  A  man  of  common  mind  would  have 
rested  satisfied  with  this  success.  Watt,  on  the  contrary, 
as  usual  with  him,  saw  cause  in  it  for  deep  study.  His 
researches  were  successively  directed  to  all  the  points 
that  appeared  likely  to  clear  up  the  theory  of  the  ma- 
chine. He  ascertained  the  proportion  in  which  water 
dilates  in  passing  from  a  state  of  fluidity  into  that  of 
vapour  ;  the  quantity  of  water  that  a  certain  weight  of 
coal  can  convert  into  vapour  ;  the  quantity  and  weight 
of  steam  expended  at  each  oscillation  by  one  of  Newco- 


watt's  labours  in  the  steam-engine.      389 

men's  engines  of  known  dimensions  ;  the  quantity  of 
cold  water  that  must  be  injected  into  the  cylinder  to 
give  a  certain  force  to  the  piston's  descending  oscillation  ; 
and  finally  the  elasticity  of  steam  at  various  tempera- 
tures. 

Hei'e  was  enough  to  occupy  the  life  of  a  laborious 
physicist,  yet  Watt  found  means  to  conduct  all  these 
numerous  and  difficult  researches  to  a  good  termination, 
without  the  work  of  the  shop  suffering  thereby.  Dr. 
Cleland  wished,  not  long  since,  to  take  me  to  the  house, 
near  the  port  of  Glasgow,  whither  our  associate  retired 
on  quitting  his  tools,  to  become  an  experimenter.  It  was 
razed  to  the  ground  !  Our  anger  was  keen  but  of  short 
duration.  Within  the  area,  still  visible  of  the  founda- 
tions, ten  or  twelve  vigorous  workmen  appeared  to  be 
occupied  in  sanctifying  the  cradle  of  modern  steam- 
engines  ;  they  were  hammering  with  redoubled  blows 
various  portions  of  boilers,  the  united  dimensions  of 
which  certainly  equalled  those  of  the  humble  dwelling 
that  had  disappeared  there.  On  such  a  spot,  and  under 
such  circumstances,  the  most  elegant  mansion,  the  most 
sumptuous  monument,  the  finest  statue,  would  have 
awakened  less  reflection  than  those  colossal  boilers. 

If  the  properties  of  steam  are  still  present  to  your 
mind,  you  will  perceive  at  a  glance,  that  the  economic 
working  of  Newcomen's  engine  seems  to  require  two 
irreconcilable  conditions.  When  the  piston  descends, 
the  cylinder  is  required  to  be  cold,  otherwise  it  meets 
some  steam  there,  still  very  elastic,  which  retards  the 
operation  very  much,  and  diminishes  the  effect  of  the 
external  atmosphere.  Then,  when  steam  at  the  temper- 
ature of  100°  flows  into  that  same  cylinder  and  finds  it 
cold,  the  steam  restores  its  heat  by  becoming  partially 


390  JAMES    WATT. 

fluid,  and  until  the  cylinder  has  regained  the  temperature 
of  100°,  its  elasticity  will  be  found  considerably  attenu- 
ated ;  thence  will  ensue  slowness  of  motion,  for  the  coun- 
terpoise will  not  raise  the  piston  until  there  is  sufhcient 
spring  contained  in  the  cylinder  to  counterbalance  the 
action  of  the  atmosphere  ;  thence  there  will  also  arise  aa 
increase  of  expense,  for,  as  I  have  already  said,  the  price 
of  steam  is  very  high.  No  doubt  will  remain  on  the  im- 
mense importance  of  this  economical  consideration,  when 
I  shall  have  stated  that  the  Glasgow  model  at  each  oscil- 
lation expended  a  volume  of  steam  several  times  larger 
than  that  of  the  cylinder.  The  expense  of  steam,  or, 
what  comes  to  the  same  thing,  the  expense  of  fuel,  or,  if 
we  like  it  better,  the  pecuniary  cost  of  keeping  on  the 
working  of  the  machine,  would  be  several  times  less  if 
the  successive  heatings  and  coolings,  the  inconveniences 
of  which  have  just  been  described,  could  be  avoided. 

This  apparently  insolvable  problem  was  solved  by  Watt 
in  the  most  simple  manner.  It  sufficed  for  him  to  add  to 
the  former  arrangement  of  the  engine  a  vessel  totally  dis- 
tinct from  the  cylinder,  and  communicating  with  it  only 
by  a  small  tube  furnished  with  a  tap.  This  vessel,  now 
known  as  the  condenser,  is  Watt's  principal  invention. 
Notwithstanding  ray  earnest  wish  to  abridge,  I  feel  that 
I  must  explain  its  mode  of  action. 

If  there  be  a  free  communication  between  a  cylinder 
full  of  steam  and  a  vessel  containing  neither  steam  nor 
air,  the  steam  from  the  cylinder  will  partly  and  very 
rapidly  pass  into  the  empty  vessel ;  the  passage  will  only 
cease  when  the  elasticity  becomes  equal  in  both.  Let  us 
suppose  that  by  an  abundant  and  constant  injection  of 
water,  the  whole  capacity  and  the  sides  of  the  vessel  be 
kept  constantly  cold,  then   the   steam  will  condense  as 


THE    CONDENSER    INTRODUCED.  391 

soon  as  it  enters  ;  all  the  steam  which  before  filled  the 
cylinder  will  be  gradually  annihilated ;  the  cylinder  will 
thus  be  cleared  of  steam  without  its  sides  being  in  the 
least  cooled,  and  the  fresh  supply  of  steam,  with  which 
it  will  require  to  be  filled,  will  not  lose  any  of  its  elas- 
ticity. 

The  condenser  attracts  to  itself  all  the  steam  contained 
in  the  cylinder,  partly  because  it  contains  some  cold 
water,  and  partly  because  is  contains  no  elastic  fluids  ; 
but  as  soon  as  some  steam  has  been  condensed,  those  two 
conditions  on  which  success  depended  have  disappeared  ; 
the  condensing  water  has  become  hot  by  absorbing  the 
latent  caloric  of  the  steam  ;  a  considerable  portion  of 
steam  has  been  generated  at  the  expense  of  that  hot 
water  ;  the  cold  water  contained  besides  some  atmos- 
pheric air  whicl*  must  have  been  disengaged  during  its 
heating.  If  this  hot  water  was  not  carried  away  after 
each  operation,  together  with  the  steam  and  the  air  con- 
tained in  the  condenser,  in  the  end  no  effect  would  be 
produced.  Watt,  therefore,  attains  this  triple  purpose  by 
the  aid  of  a  common  pump,  called  an  air-pump,  and  the 
piston  of  which  carries  a  rod  suitably  attached  to  the 
beam  worked  by  the  engine.  The  power  intended  to 
keep  the  air-pump  in  motion,  diminishes  by  that  much 
the  power  of  the  engine ;  but  it  is  only  a  small  portion  of 
the  loss  that  was  occasioned,  in  the  old  arrangement,  by 
the  steam  being  condensed  on  the  refrigerated  sui'face  of 
the  body  of  the  engine. 

Still  another  invention  by  Watt  deserves  a  word,  the 
advantages  of  which  will  become  evident  to  everybody. 

When  the  piston  descends  in  Newcomen's  engine,  it  is 
by  tlie  weight  of  the  atmosphere.  The  atmosphere  is 
cold,  hence  it  must  cool  the  sides  of  the  metal  cylinder, 


392  JAMES    WATT. 

which  is  open  at  the  top,  in  proportion  as  it  expands 
itself  over  their  entire  surface.  This  cooling  is  not  com- 
pensated during  the  whole  ascension  of  the  piston,  with- 
out the  expense  of  a  certain  quantity  of  steam.  But 
there  is  no  loss  of  this  sort  in  the  engines  modified  by 
Watt.  The  atmospheric  action  is  totally  eliminated  by 
the  following  means  : — 

The  top  of  the  cylinder  is  closed  by  a  metal  cover, 
only  pierced  in  the  centre  by  a  hole  furnished  with 
greased  tow  stuffed  in  hard,  but  through  which  the  rod  of 
the  piston  has  free  motion,  though  without  allowing  free 
passage  either  to  air  or  steam.  The  piston  thus  divides 
the  capacity  of  the  cylinder  into  two  distinct  and  well- 
closed  areas.  When  it  has  to  descend,  the  steam  from 
the  caldron  reaches  freely  the  upper  area  through  a  tube 
conveniently  placed,  and  pushes  it  from*top  to  bottom  as 
the  atmosphere  did  in  Newcomen's  engine.  There  is  no 
obstacle  to  this  motion,  because  whilst  it  is  going  on,  only 
the  base  of  the  cylinder  is  in  communication  with  the 
condenser,  wherein  all  the  steam  from  that  lower  area 
resumes  its  fluid  state.  As  soon  as  the  piston  has  quite 
reached  the  bottom,  the  mere  turning  of  a  tap  suffices  to 
bring  the  two  areas  of  the  cylinder,  situated  above  and 
below  the  piston,  into  communication  with  each  other, 
so  that  both  shall  be  filled  with  steam  of  the  same  degree 
of  elasticity,  and  the  piston  being  thus  equally  acted  upon, 
upwards  and  downwards,  ascends  again  to  the  top  of  the 
cylinder,  as  in  Newcomen's  atmospheric  engine,  merely 
by  the  action  of  a  slight  counterpoise. 

Pursuing  his  researches  on  the  means  of  economizing 
steam,  Watt  also  reduced  the  result  of  the  refrigeration 
of  the  external  surface  of  the  cylinder  containing  ihe  pis- 
ton, almost  to  nothing.     With  this  view  he  enclosed  the 


COMPLETION    OP    IIIS    ENGINE.  393 

metal  cylinder  in  a  wooden  case  of  larger  diameter,  filling 
the  intermediate  annular  space  with  steam.* 

Now  the  engine  was  complete.  The  improvements 
effected  by  Watt  are  evident ;  there  can  be  no  doubt  of 
their  immense  utility.  As  a  means  of  drainage,  then, 
you  would  expect  to  see  them  substituted  for  Newco- 
men's  comparatively  ruinous  engines.  Undeceive  your- 
selves :  the  author  of  a  discovery  has  always  to  contend 
against  those  whose  interest  may  be  injured,  the  obstinate 
partisans  of  every  thing  old,  and  finally,  the  envious. 
And  these  three  classes  united,  I  regret  to  acknowledge 
it,  form  the  great  majority  of  the  public.  In  my  calcu- 
lation I  even  deduct  those  who  are  doubly  influenced  to 
avoid  a  paradoxical  result.  This  compact  mass  of  oppo- 
nents can  only  be  disunited  and  dissipated  by  time  ;  yet 
time  is  insufficient,  it  must  be  attacked  with  spirit  and 
unceasingly ;  our  means  of  attack  must  be  varied,  imitat- 
ing the  chemist  in  this  respect, — he  learning  from  ex- 
perience, that  the  entire  solution  of  certain  amalgams 
requires  the  successive  application  of  several  acids. 
Force  of  character  and  perseverance  of  will,  which  in 
the  long  run  disintegrate  the  best  woven  intrigues,  are 
not  always  found  conjoined  with  creative  genius.  In 
case  of  need,  Watt  would  be  a  convincing  proof  of  this. 
His  capital  invention — his  happy  idea  on  the  possibility 

*  It  is  the  cylinder  and  piston  that  constitute  the  eminent  virtue 
of  the  engine,  the  steam  being  only  the  agent  employed  to  work  the 
pump,  so  to  speak.  Every  modification,  therefore,  which  can  promote 
the  action  of  this  most  convenient  and  powerful  agent  is  a  crucial  ad- 
vantage. It  is,  therefore,  that  the  vast  improvements  made  by  Watt 
—not  only  in  working  the  piston-rod  in  the  aperture  of  the  stuffing- 
box,  but  also  in  promoting  the  uniform  warmth  of  the  cylinder  by  a 
jacket  or  outer  casing— brought  the  steam-engine  substantially  to  its 
present  rank. —  Trantlaior. 

17  * 


394  JAMES    WATT. 

of  condensing  steam  in  a  vessel  separate  from  the  cylin- 
der in  which    the    mechanical  action   goes  on — was  in 
17G5.     Two  years  elapsed  without  his  scarcely  making 
an  effort  to  apply  it  on  a  large  scale.     His  friends  at  last 
put  him  in  communication  with  Dr.  Roebuck,  founder  of 
the  large  works  at  Carron,  still  celebrated  at  the  present 
day.     The  engineer  and  the  man  of  projects  enter  into 
partnership  ;  Watt  cedes  two  thirds  of  his  patent  to  him. 
An  engine  is  constructed  on  the  new  principles :  it  con- 
firms all  the  expectations  of  theory  ;  its  success  is  com- 
plete.    But  in  the  interim,  Dr.  Roebuck's  affairs  receive 
various   checks.      Watt's   invention  would   undoubtedly 
have  restored  them  :   it  would  have  sufficed  to  borrow 
money ;  but  our  associate  felt  more  inclined  to  give  up 
his  discovery  and  change  his  business.     In  17G7,  while 
Smeaton  was  carrying  on  some  triangulations  and  level- 
lings  between  the  two  rivers  of  the  Forth  and  the  Clyde, 
forerunners  of  the  gigantic  works  of  which  that  part  of 
Scotland  was  to  be  the  theatre,  we  find  Watt  occupied 
with  similar  operations  along  a  rival  line  crossing  the 
Lomond  passage.     Later,  he  draws  the  plan  of  a  canal 
that  was  to  bring  coals  from  Monkland  to  Glasgow,  and 
superintends  the  execution  of  it.     Several  projects  of  a 
similar  nature,  and,  among  others,  that  of  a  navigable 
canal  across  the  Isthmus  of  Crinan,  which  Mr.  Rennie 
afterwards   finished  ;   some  deep  studies  on  certain  im- 
provements in  the  ports  of  Ayr,  Glasgow,  and  Greenock  ; 
the  construction  of  the  Hamilton  and  Rutherglen  bridges  ; 
surveys  of  the  ground  througli  which  the  celebrated  Cale- 
donian Canal  was  to  pass,  occupied  our  associate  up  to 
the  end  of  1773.     Without  wishing  at  all  to  diminish  the 
merit  of  these  enterprises,  I  may  be  permitted  to  say  that 
their  interest  and  importance  was  chiefly  local,  and  to 


ANNOYANCES.  395 

assert  that  neither  their  conception,  direction,  nor  execu- 
tion required  a  man  called  James  Watt. 

If  I  were  to  forget  my  duties  as  the  mouthpiece  of  the 
Academy,  and  endeavour  more  to  make  you  smile  than 
try  to  relate  useful  truths,  I  should  find  matter  here  for 
a  striking  contrast.  I  might  cite  this  or  that  author 
who,  at  our  weekly  meetings,  labours  loudly  to  commu- 
nicate some  little  remarks,  some  trifling  reminiscence, 
some  little  note,  conceived  and  got  up  the  previous  even- 
ing ;  I  might  represent  him  cursing  his  destiny,  because 
some  clause  in  the  rules,  or  the  order  of  insertion  of 
some  author,  an  earlier  riser  than  himself,  occasions  his 
lecture  to  be  deferred  for  a  week,  allowing  him  the 
guarantee,  during  the  whole  of  that  cruel  week,  of  his 
sealed  paquet  being  deposited  in  our  archives.  On  the 
other  hand,  we  should  see  the  inventor  of  a  machine 
destined  to  form  an  epoch  in  the  annals  of  the  world, 
undergo  without  a  murmur  the  stupid  contempt  of 
capitalists,  and  during  eight  years  bend  his  superior 
genius  down  to  surveys,  plans,  and  minute  levellings ;  to 
troublesome  items  of  clearing  or  filling  in,  and  to  toises 
of  masonry.  Let  us  confine  ourselves  to  supposing  that 
Watt's  philosophy  led  to  serenity  of  character,  modera- 
tion in  desires,  to  true  modesty.  But  so  much  indiffer- 
ence, however  noble  the  cause  may  have  been,  should 
have  its  just  limit.  It  is  not  without  ample  motive  that 
society  severely  reprobates  those  of  its  members  who 
withdraw  from  circulation  the  heaps  of  gold  contained  in 
their  iron  chests.  Are  we  less  culpable  if  we  deprive 
our  country,  our  fellow-citizens,  our  century,  of  the 
treasures,  a  thousand  times  more  precious,  resulting 
from  the  exercise  of  mind  ;  if  we  keep  to  ourselves 
immortal  inventions,  sources  of  the   most  noble,  of  the 


396  JAMES    WATT. 

purest  enjoyments  of  intellect ;  if  we  do  not  reward  the 
creators  of  mechanical  combinations,  which  would  mul- 
tiply the  products  of  industry  to  infinity  ;  who  would 
weaken,  to  the  benefit  of  civilization  and  humanity,  the 
effect  of  the  difference  of  position ;  who  would  some  day 
allow  the  rudest  manufactories  to  be  examined  without 
finding,  in  any  part  of  them,  the  distressing  spectacle  of 
fathers  of  families  and  children  of  both  sexes  assimilated 
to  brutes,  advancing  precipitately  to  their  tombs  ? 

In  the  early  part  of  1774,  after  contending  with  Watt's 
indifference,  his  friends  put  him  into  communication  with 
Mr.  Boulton,  of  Soho,  near  Birmingham  ;  an  enterpris- 
ing active  man,  gifted  with  various  talents.*     The  two 

*  In  the  notes  which  accompanied  the  last  edition  of  Professor 
Eobison's  Essay  on  the  Steam-engine,  Watt  expressed  himself  in  the 
following  terms  relative  to  Mr.  Boulton :  "  The  friendship  that  he 
bore  me  ended  only  with  his  life.  The  friendship  that  I  bore  him 
leads  me  to  feel  it  my  duty  to  avail  myself  of  this  opportunity,  the 
last,  probably,  that  will  be  offered  me,  to  say  how  much  I  was  in- 
debted to  him.  It  is  to  the  earnest  encouragement  held  out  to  me  by 
Mr.  Boulton,  to  his  taste  for  scientific  discoveries,  and  to  the  sagacity 
with  which  he  applied  them  to  the  progress  of  the  arts ;  it  is  also  to  the 
intimate  knowledge  he  possessed  of  manufacturing  and  commercial 
affairs,  that  I  attribute,  in  great  measure,  the  success  with  which  my 
efforts  have  been  crowned." 

Mr.  Boulton  had  already  had  a  manufoctory  for  several  years  at 
Soho,  when  the  partnership  began  which  has  rendered  his  name  so 
inseparable  from  that  of  Watt.  This  establishment,  the  first  that 
had  been  formed  on  so  large  a  scale  in  England,  is  still  quoted  for  its 
elegant  architecture.  Boulton  used  to  make  there  all  sorts  of  work  in 
steel,  in  plated  articles,  in  silver,  in  or  moulu ;  even  to  astronomical 
clocks,  and  paintings  on  glass.  During  the  last  twenty  years  of  his 
life,  Boulton  occupied  himself  with  improving  the  coining  of  money. 
By  the  combination  of  some  operations  invented  in  France,  with  new 
presses  and  an  ingenious  application  of  the  steam-engine,  he  con- 
trived to  unite  an  exceeding  rapidity  of  performance  with  perfection 
of  work.  It  was  Boulton  who  executed  for  the  English  Government 
the  recoining  of  the  whole  copper  currency  in  the  United  Kingdom. 


PROLONGATION  OF  THE  PATENT.       397 

friends  applied  to  Parliament  for  a  prolongation  of  privi- 
lege ;  since  Watt's  Patent,  dated  1769,  had  only  a  few 
more  years  to  run.  The  bill  gave  rise  to  the  most 
animated  discussion.  The  celebrated  mechanic  wrote  as 
follows  to  his  aged  father :  "  This  business  could  not  be 
carried  on  without  great  expense  and  anxiety.  With- 
out the  aid  of  some  warm-hearted  friends,  we  should  not 
have  succeeded,  for  several  of  the  most  powerful  people 
in  the  House  of  Commons  were  opposed  to  us."  It 
seemed  to  me  interesting  to  search  out  to  what  class  of 
society  these  Parliamentary  persons  belonged,  to  whom 
Watt  alluded,  and  Avho  refused  to  the  man  of  genius  a 
small  portion  of  the  riches  that  he  was  about  to  create. 
Judge  of  my  surprise,  when  I  found  the  celebrated 
Burke  at  their  head  !  Is  it  possible  then  that  men  may 
devote  themselves  to  deep  studies,  possess  knowledge 
and  probity,  exercise  to  an  eminent  degree  oratorical 
powers  that  move  the  feelings,  and  influence  political 
assemblies,  yet  sometimes  be  deficient  in  plain  common 
sense  ?  Now,  however,  owing  to  the  wise  and  important 
modifications  introduced  by  Lord  Brougham  in  the  laws 
relative  to  patents,  inventors  will  no  longer  have  to 
undergo  the  annoyances  with  which  Watt  was  teased. 

As  soon  as  Parliament  had  granted  a  prolongation  of 
twenty-five  years  to  Watt's  patent,  he  and  Boulton 
together  began  the  establishments  at  Soho,  which  have 

The  economy  and  correctness  of  this  great  work  rendered  counter- 
feiting almost  impossible.  The  numerous  executions  with  which  the 
towns  of  London  and  Birmingham  had  been  annually  afflicted  till 
then,  entirely  ceased.  It  was  on  this  occasion  that  Dr.  Darwin  ex- 
claimed in  his  Botanical  Garden,  "  If  at  Rome  a  civic  crown  was 
awarded  to  those  who  had  saved  the  life  of  a  single  fellow-citizen,  did 
not  Boulton  deserve  to  be  covered  with  crowns  of  oak  by  usV  " 
Mr.  Boulton  died  in  1809,  at  the  age  of  eighty-one  years. 


398  JAMES    WATT. 

become  the  most  useful  school  in  practical  mechanics  for 
all  England.  The  construction  of  draining  pumps  of 
very  large  dimensions  was  soon  undertaken  there,  and 
repeated  experiments  showed  that,  with  equal  effect, 
they  saved  three  quarters  of  the  fuel  that  was  consumed 
by  Newcomen's  previous  engines.  From  that  moment 
the  new  pumps  were  spread  through  all  the  mining 
counties,  especially  in  Cornwall.  Boulton  and  Watt 
received  as  a  duty  the  value  of  one  third  of  the  coal 
saved  by  each  of  their  engines.  We  may  form  an 
opinion  of  the  commercial  importance  of  the  invention 
from  an  authentic  fact ;  in  the  Chace-water  Mine  alone, 
where  three  pumps  were  at  work,  the  pi'oprietors  found 
it  to  their  advantage  to  buy  up  the  inventor's  rights  for 
the  annual  sum  of  60,000  francs  (£2,400).  Thus  in 
one  establishment  alone,  the  substitution  of  the  condenser 
for  internal  injection,  had  occasioned  an  annual  saving 
in  fuel  of  upwards  of  180,000  francs  (£7,000).* 

Men  are  easily  reconciled  to  paying  the  rent  of  a 
house,  or  the  price  of  a  farm.  But  this  good-will  disap- 
pears when  an  idea  is  the  subject  treated  of,  whatever 
advantage,  whatever  profit,  it  may  be  the  means  of  pro- 
curing. Ideas  !  are  they  not  conceived  without  ti'ouble 
or  labour  ?  Who  can  prove  but  that  with  time  the  same 
might  not  have  occurred  to  everybody  ?  In  this  way 
days,  months,  and  years  of  priority  would  give  no  force 
to  a  patent ! 

Such  opinions,  which   I  need  not  here  criticize,  had 

obtained  a  footing  from  mere  routine,  as  decided.     Men 

*  Here  it  must  be  borne  in  mind  that  a  principal  method  of  insur- 
ing a  return  for  their  outlay,  was  their  manufacturing  steam-engines 
on  the  most  extensive  scale,  with  a  degree  of  accuracy  never  before 
applied  in  the  production  of  large  machinery;  and  this  was  so  fully 
accomplished,  that  all  other  engines  were  superseded. —  Tramlator. 


EXPENSIVE    LAWSUITS.  399 

of  genius,  the  manufacturers  of  ideas,  it  seemed,  were 
to  remain  strangers  to  material  enjoyments ;  it  Avas 
natural  that  their  history  should  continue  to  resemble  a 
legend  of  martyrs  ! 

Whatever  may  be  thought  of  these  reflections,  it  is 
certain  that  the  Cornwall  miners  paid  the  dues  that  were 
granted  to  the  Soho  engineers  with  increased  repugnance 
from  year  to  year.  They  availed  themselves  of  the  very 
earliest  difficulties  raised  by  plagiarists,  to  claim  release 
from  all  obligation.  The  discussion  was  serious ;  it 
might  compromise  the  social  position  of  our  associate  ; 
he  therefore  bestowed  his  entire  attention  to  it,  and  be- 
came a  lawyer.  The  long  and  expensive  lawsuits  that 
resulted  therefrom,  but  which  they  finally  gained,  Avould 
not  deserve  to  be  now  exhumed ;  but  having  recently 
quoted  Burke  as  one  of  the  adversaries  to  our  great 
mechanic,  it  appears  only  a  just  compensation  here  to 
mention  that  the  Roys,  Mylnes,  Herschels,  Delucs, 
Eamsdens,  Robisons,  Murdocks,  Rennies,  Cummings, 
Mores,  Southerns,  eagerly  presented  themselves  before 
the  magistrates,  to  maintain  the  rights  of  persecuted 
genius.  It  may  be  also  advisable  to  add,  as  a  curious 
trait  in  the  history  of  the  human  mind,  that  the  lawyers 
(I  shall  here  prudently  remark  that  we  treat  only  of  the 
lawyers  of  a  neighbouring  country),  to  whom  malignity 
imputes  a  superabundant  luxury  in  words,  reproached 
Watt,  against  whom  they  had  leagued  in  great  numbers, 
for  having  invented  nothing  but  ideas.  This,  I  may 
remark  in  passing,  brought  upon  them  before  the  tribu- 
nal, the  following  apostrophe  from  Mi-.  Rous  :  *    "  Go, 

*  Mr.  Rous,  who  acted  as  counsel  for  the  patentees,  published  his 
speech  in  the  form  of  a  pamphlet.  In  the  text  we  have  reproduced 
the  English  from  a  version  of  M.  Arago's  French,  an  unsatisfactory 


400  JAMES    WATT. 

gentlemen,  go  and  rub  yourselves  against  those  untangible 
combinations,  as  you  are  j^leased  to  call  Watt's  engines — 
against  those  pretended  abstract  ideas  ;  they  will  crush 
you  like  gnats,  they  will  hurl  you  up  in  the  air  out  of 
sight  !  " 

The  persecutions  which  a  warm-hearted  man  meets 
with,  in  the  quarters  where  strict  justice  would  lead  him 
to  expect  unanimous  testimonies  of  gratitude,  seldom  fail 
to  discourage,  and  to  sour  his  disposition.  Nor  did  Watt's 
good  humour  remain  proof  against  such  trials.  Seven 
long  years  of  lawsuits  had  excited  in  him  such  a  senti- 
ment of  indignation,  that  it  occasionally  showed  itself  in 
severe  expressions  ;  thus  he  wrote  to  one  of  his  friends  : 
— "  What  I  most  detest  in  this  world  are  plagiarists. 
The  plagiarists  !  They  have  already  cruelly  assailed  me ; 
and  if  I  had  not  an  excellent  memory,  their  impudent  as- 
sertions would  have  ended  by  persuading  me  that  I  have 
made  no  improvement  in  steam-engines.  The  bad  pas- 
sions of  those  men  to  whom  I  have  been  most  useful — 
would  you  believe  it  ?  have  gone  so  far  as  to  lead  them 
to  maintain  that  those  improvements,  instead  of  deserving 
this  denomination,  have  been  highly  prejudicial  to  public 
wealth." 

practice  arising  from  necessity;  for,  in  his  full  acquaintance  ■with  our 
writings,  he  is  exuberant  in  quotations  without  always  giving  chap- 
ter and  verse ;  and,  moreover,  many  of  the  cited  passages  are  from 
letters  and  other  manuscript  documents.  In  the  instance  before  us, 
the  keen  satire  of  Rous  was  in  asking  the  opposite  party  whether  it 
could  be  seriously  contended  that  Watt's  invention,  which,  during  the 
space  of  nearlj'  thirty  years,  had  been  admired  in  all  Europe  as  the 
greatest  jiractical  advance  ever  made  in  the  arts,  was  a  mere  ahstract 
discovery  in  science  ;  and,  he  observed,  that  if  those  who  thus  pleaded 
were  to  approach  the  untancjible  substance,  as  they  were  pleased  to  call 
it,  with  the  same  ignorance  of  its  nature  that  they  thus  affected,  they 
would  be  crushed  before  it  like  flies,  leaving  no  trace  of  their  exist- 
ence.—  Translator. 


DOUBLE-ACTING    ENGINES.  401 

Watt,  though  greatly  irritated,  was  not  discouraged. 
His  engines  were  not,  in  the  first  place,  like  Newco- 
men's,  mere  pumps,  mere  di-aining  pumps.  In  a  few 
years  he  transformed  them  into  universal  motive  pow- 
ers, and  of  indefinite  force.  His  first  step  in  this  line 
was  the  invention  of  a  double-acting  engine  (a  double 
effet). 

To  conceive  the  principle  of  it,  let  my  report  of  the 
modified  engine  of  which  I  have  already  treated  (page 
391,)  be  consulted.  The  cylinder  is  closed ;  the  ex- 
ternal air  has  no  access  to  it ;  it  is  steam  pressure,  and 
not  atmospheric,  that  makes  the  piston  descend ;  the 
ascending  movement  is  due  to  a  simple  counterpoise,  be- 
cause at  the  moment  when  this  takes  place,  the  steam, 
being  enabled  to  circulate  freely  from  the  higher  to  the 
lower  portions  of  the  cylinder,  presses  equally  on  the 
piston  in  both  directions.  Every  one  will  hence  see,  that 
the  modified  engine,  or  Newcomen's,  has  power  only 
during  the  descending  oscillation  of  the  piston. 

A  very  simple  change  remedied  this  serious  defect,  and 
produced  the  double-acting  engine. 

In  the  engine  known  under  this  name,  as  well  as  in 
the  one  which  we  denominated  the  modified  engine,  the 
steam  from  the  boiler,  when  the  mechanic  wishes  it,  goes 
freely  above  the  piston  and  presses  it  down  without 
meeting  any  obstacle;  because  at  that  same  moment, 
the  lower  area  of  the  cylinder  is  in  communication  with 
the  condenser.  This  movement  once  achieved,  and  a 
certain  cock  having  been  opened,  the  steam  from  the 
caldron  can  enter  only  below  the  piston,  and  elevates  it ; 
the  steam  above  it,  which  had  produced  the  descending 
movement,  then  goes  to  regain  its  fluid  state  in  the  con- 
denser, with  which  it  has  become,  in   its   turn,  in   free 


402  JAMES    WATT. 

communication.  The  contrary  arrangement  of  the  cocks 
replaces  all  things  in  their  primitive  state,  as  soon  as  the 
piston  has  regained  its  maximum  height.  Thus  similar 
effects  are  reproduced  indetinitely. 

The  motive  power  is  here,  as  explained  above,  exclu- 
sively steam ;  and  the  engine,  except  by  the  inequality 
arising  from  the  weight  of  the  piston,  has  the  same  power 
whether  the  piston  be  ascending  or  descending.  This  is 
the  reason  why,  from  the  moment  of  its  appearance  it  w^as 
justly  called  a  donhle-acting  engine. 

To  render  this  new  motive  power  of  easy  and  conve- 
nient application,  Watt  had  to  overcome  other  difficulties  : 
it  was  requisite  to  find  the  means  of  establishing  a  rigid 
communication  between  the  inflexible  rod  of  the  piston 
oscillating  in  a  straight  line  and  a  beam  that  oscillated 
circularly.  The  solution  which  he  gave  of  this  important 
problem  is  perhaps  his  most  ingenious  invention. 

Among  the  constituent  parts  of  a  steam-engine,  you 
have,  no  doubt,  remarked  a  certain  articulated  parallelo- 
gram. With  each  double  oscillation  it  develops  and  con- 
tracts itself,  with  the  smoothness  of  motion, — I  had 
almost  said  with  the  grace, — that  charms  us  in  the  ges- 
tures of  a  consummate  actor.  Follow  attentively  with 
your  eye  its  various  transformations,  and  you  will  find  it 
subject  to  the  most  curious  geometrical  conditions  ;  that 
three  of  the  summits  of  the  parallelogram's  angles  describe 
arcs  of  circles  in  space,  whilst  the  fourth,  the  summit  of 
the  angle  that  raises  and  lowers  the  piston-rod,  moves 
very  nearly  in  a  straight  line.  The  immense  utility  of 
the  result  strikes  mechanics  less  than  the  simplicity  of 
means  by  which  Watt  obtained  it.* 

*  We  here  give  Watt's  words  in  relating  the  experiment  of  this  artic- 
ulated parallelogram  {Ms  beautiful  arranijement  is  called  parallel  mo- 


THROTTLE  VALVE  AND  GOVERNOR.      403 

Power  is  not  the  only  element  of  success  in  industrial 
worivs.  Regularity  of  action  is  not  less  important ;  but 
what  regularity  could  be  expected  from  a  motive  power 
engendered  by  fire  fed  by  shovels  full,  and  the  coal  itself 
of  various  qualities  ;  and  this  under  the  direction  of  a 
workman,  sometimes  not  very  intelligent,  almost  always 
inattentive  ?  The  motive  steam  will  be  more  abundant, 
it  will  flow  more  rapidly  into  the  cylinder,  it  will  make 
the  piston  work  faster  in  proportion  as  the  fire  is 
more  intense.  Great  inequalities  of  movement  then  ap- 
pear to  be  inevitable.  Watt's  genius  had  to  provide 
against  this  serious  defect.  The  throttle-valves  by  which 
the  steam  issues  from  the  boiler  to  enter  the  cylinder  are 
not  constantly  open.  When  the  working  of  the  engine 
accelerates,  these  valves  partly  close ;  a  certain  vol- 
ume of  steam  must  therefore  occupy  a  longer  time  in 
passing  through  them,  and  the  acceleration  ceases.  The 
aperture  of  the  valves,  on  the  conti-ary,  dilates  when  the 
motion  slackens.  The  pieces  requisite  for  the  perform- 
ance of  these  various  changes  connect  the  valves  with 
the  axes  which  the  engine  sets  to  woi*k,  by  the  introduc- 

tion — Translator):  "I  was  myself  surprised  at  the  regularity  of  its 
action.  When  I  saw  it  work  for  the  first  time,  I  felt  truly  all  the 
pleasure  of  novelty,  as  if  I  was  examining  the  invention  of  another 
man." 

SmeatOD,  who  was  a  great  admirer  of  Watt,  did  not  believe,  how- 
ever, that  it  could  in  practice  become  a  general  and  economical 
means  of  impressing  directly  rotatory  motion  to  axes.  He  maintained 
that  steam-engines  would  always  be  more  serviceable  in  pumping 
water  direct.  This  fluid  having  reached  a  suitable  height,  was  then  to 
be  thrown  into  the  trough,  or  on  to  the  pallets  of  common  hydraulic 
wheels.  In  this  respect  the  prophecies  of  Smeaton  were  not  realized. 
Yet,  in  1834,  on  visiting  the  establishment  of  Mr.  Boulton  at  Soho,  I 
saw  an  old  steam-engine  still  employed  to  raise  water  from  a  large 
pool,  and  pour  it  into  the  troughs  of  a  great  hydraulic  wheel,  when 
the  season  being  ver}-  dry  the  water-power  was  insufficient. 


404  JAMES    ■\VATT. 

tion  of  an  apparatus,  the  principle  of  which  Watt  dis- 
covered in  the  reguhxtor  of  the  sails  of  some  flour-mills  : 
this  he  named  the  governor;  which  is  now  called  the 
centrifugal  regulator.  Its  efficacy  is  such,  that  a  few 
years  ago  in  the  cotton-spinning  manufactory  of  a  re- 
nowned mechanic,  Mr.  Lee,  there  was  a  clock  set  in 
motion  by  the  engine  of  the  establishment,  and  it  showed 
no  great  inferiority  to  a  common  spring  clock. 

Watt's  regulator,  and  an  intelligent  use  of  the  re- 
volving principle, — that  is  the  secret,  the  true  secret,  of 
the  astonishing  perfection  of  the  industrial  products  of 
our  epoch ;  this  is  what  now  gives  to  the  steam-engine 
a  rate  entirely  free  from  jerks.  That  is  the  reason  why 
it  can,  with  equal  success,  embroider  muslins  and  forge 
anchors, -weave  the  most  delicate  webs  and  communicate 
a  rapid  movement  to  the  heavy  stones  of  a  flour-mill. 
This  also  explains  how  Watt  had  said,  fearless  of  being 
reproached  for  exaggeration,  that  to  prevent  the  comings 
and  goings  of  servants,  he  would  be  served,  he  would 
have  gruel  brought  to  him,  in  case  of  illness,  by  tablets 
connected  with  his  steam-engine.  I  am  aware  it  is  sup- 
posed by  the  generality  of  people,  that  this  suavity  of 
motion  is  obtained  only  by  a  loss  of  power ;  but  it  is  an 
error,  a  gross  error :  the  saying,  "  nmch  noise  and  little 
work,"  is  true  not  only  in  the  moral  world,  but  is  also  an 
axiom  in  mechanics. 

A  few  words  more  and  we  shall  reach  the  end  of  our 
technical  details. 

Within  these  few  years,  great  advantage  has  been 
found  in  not  allowing  a  free  access  of  steam  from  the 
boiler  into  the  cylinder,  during  the  ivhole  time  of  each 
oscillation  of  the  engine.*     This  communication  is  inter- 

*  This  constituted  Watt's  celebrated  expansion  engine,  so  named 


STEAM    DETENTION.  405 

riipted,  for  example,  when  the  piston  has  reached  one 
third  of  its  course.  The  two  remaining  thirds  of  the 
cyHnder's  length  are  then  traversed  by  virtue  of  the  ac- 
quired velocity,  and  especially  by  the  detention  of  the 
steam.  Watt  had  already  indicated  such  an  arrange- 
ment.* Some  very  good  judges  esteem  the  economical 
importance  of  the  steam-detent  as  equal  to  that  of  the 
condenser.  It  seems  certain  that  since  its  adoption,  the 
Cornwall  engines  give  unhoped-for  results  ;  that  with  one 
bushel  of  coals  they  equal  the  labour  of  twenty  men 
during  ten  hours.  Let  us  keep  in  mind,  that  in  the  coal 
districts  a  bushel  of  coals  only  costs  ninepence,  and  it 
will  be  demonstrated  that  over  the  greater  part  of  Eng- 
land, Watt  reduced  the  price  of  a  man's  day's  work,  a 
day  of  ten  hours'  labour,  to  less  than  a  sou  (one  half- 
penny,) of  our  money.f 

because  the  small  portion  of  steam  already  admitterl,  then  expanded 
till  the  piston  had  reached  the  end  of  tiie  cylinder. —  Translator. 

*  The  principle  of  the  steam  detention  had  been  neatly  expressed 
in  a  letter  from  Watt  to  Dr.  Small  dated  1769,  it  was  put  in  practice 
in  1776,  at  Soho,  and  also  in  1778  at  the  Shadwell  leater  works,  from 
economical  considerations.  The  invention,  and  the  advantages  ex- 
pected from  it,  are  fully  described  in  the  patent  of  1782. 

t  At  a  moment  when  so  many  people  are  interested  in  direct  rota- 
tion engines,  I  should  be  unpardonably  neglectful  if  I  did  not  say  that 
Watt  had  both  thought  of  them,  as  proved  in  his  patents,  and  had 
made  some.  Watt  abandoned  those  engines,  not  because  they  would 
not  work,  but  because,  in  an  economical  point  of  view,  they  appeared 
to  him  decidedly  inferior  to  the  double-acting  engines,  and  to  those 
with  rectilinear  oscillations. 

There  are  few  inventions,  large  or  small,  amongst  those  of  which 
the  steam-engine  oflers  us  such  an  admirable  assemblage,  that  have 
not  been  developed  from  some  of  Watt's  early  ideas.  Follow  up  his 
labours,  and  besides  the  important  points  which  we  have  minutely 
detailed,  you  will  see  him  propose  engines  without  condensation, 
engines  in  which  the  steam,  after  having  acted,  is  allowed  to  escape 
into  the  open  air,  for  those  localities  where  it  would  be  difficult  to 
procure  an  abundance  of  cold  water. 


406  JAMES    WATT. 

Numerical  valuations  make  us  appreciate  so  well  the 
importance  of  his  inventions,  that  I  cannot  resist  the  de- 
sire to  present  two  more  improvements.  I  borrow  them 
from  one  of  the  most  celebrated  correspondents  of  the 
Academy,  from  Mr.  John  Herschel. 

The  ascent  of  Mont  Blanc,  starting  from  the  valley  of 
Chamouni,  is  justly  considered  as  the  hardest  work  that 
a  man  can  accomplish  in  two  days.  Thus,  the  maximum 
mechanical  work  of  which  we  are  capable,  in  twice  twenty- 
four  hours,  is  measured  by  transporting  the  weight  of  our 
body  to  the  elevation  of  Mont  Blanc.  This  work,  or  its 
equivalent,  would  be  accomplished  by  a  steam-engine  in 
the  course  of  burning  one  kilogram  of  coal.  Watt  has, 
therefore,  ascertained  that  the  daily  power  of  a  man  does 
not  exceed  what  is  contained  in  half  a  kilogram  of  coal 
(1  lb.  Avs.). 

Herodotus  records  that  the  construction  of  the  great 
pyramid  of  Egypt  employed  one  hundred  thousand  men 
during  twenty  years.    The  pyramid  consists  of  calcareous 

The  detent  intended  to  be  used  in  engines  having  several  cylinders, 
-will  also  figure  among  the  projects  of  the  Soho  engineer.  He  suggests 
the  idea  of  perfectly  water-tight  pistons,  thougli  consisting  entirely  of 
pieces  of  metal.  It  was  Watt  also  who  first  had  recourse  to  mercurial 
gauges  to  appreciate  the  elasticity  of  the  steam,  both  in  the  boiler  ^nd 
in  the  condenser;  who  imagined  a  simple  and  permanent  gauge,  by 
the  aid  of  which,  and  at  a  glance,  tlie  height  of  the  water  in  the  boiler 
can  be  known;  and  who,  to  prevent  this  levol  from  ever  varying  to  an 
inconvenient  extent,  connected  the  movements  of  the  feeding-pump 
with  those  of  a  float,  which,  when  required,  was  placed  in  an  opening 
of  the  lid  of  the  engine's  principal  cylinder,  forming  a  little  indicator, 
so  combined  as  to  show  exactly  the  law  of  the  steam's  consumption 
relative  to  the  piston's  position,  &c.  If  time  permitted,  I  would  show 
Watt  not  less  clever,  or  less  fortunate,  in  his  endeavours  to  improve 
'the  boilers,  to  diminish  the  loss  of  heat,  and  to  burn  completely  the 
torrents  of  black  smoke  that  escape  from  common  chimneys,  however 
high  they  may  be  carried. 


WELFARE    OF    THE    WORKING    CLASSES.  407 

Stone  ;  its  volume  and  its  weight  can  be  easily  calculated ; 
its  weight  has  been  found  to  be  about  5,900,000  kilograms 
(nearly  5000  tons). 

To  elevate  this  weight  to  thirty-eight  metres,  which  is 
^the  pyramid's  centre  of  gravity,  it  would  require  to  burn 
8,244  hectolitres  of  coal   (cubic  metres).      Our  neigh- 
bours   have   some   foundries   where  they   consume    this 
quantity  every  week. 

MACHINES    CONSIDERED     RELATIVE    TO    THEIR    EFFECT 
ON    THE    WELFARE    OF    THE    WORKING    CLASSES.* 

Many  persons,  without  doubting  the  genius  of  Watt, 
look  on  the  inventions  for  which  the  world  is  indebted  to 
him,  and  on  the  impulse  that  they  have  given  to  indus- 
trial labours,  as  a  social  misfortune.  If  we  believed 
them,  the  adoption  of  each  new  machine  inevitably  adds 
to  the  troubles  and  miseries  of  labourers.     Those  won- 


*  In  writing  this  chapter  it  seemed  to  me  that  I  might  unscrupu- 
lously avail  myself  of  many  documents  that  I  had  collected,  either  in 
various  conversations  with  my  friend  Lord  Brougham,  or  works  that 
he  himself  has  i>ublished,  or  that  have  appeared  under  his  patronage. 

If  I  were  to  attend  to  the  criticisms  that  have  been  printed  after  the 
reading  of  this  Biography,  by  trying  to  combat  the  opinion  that  ma- 
chines are  injurious  to  the  labouring  classes,  I  should  be  attacking  an 
old  prejudice  that  has  no  longer  any  foundation,  a  mere  phantom.  I 
would  not  ask  more  than  to  be  able  to  believe  it,  for  then  I  would  very 
willingly  suppress  all  my  arguments,  bad  or  good.  Unfortunately  some 
letters  frequently  sent  me  by  excellent  workmen,  either  as  an  acade- 
mician or  as  a  deputy;  unfortunately,  moreover,  the  recent  and  ex- 
professo  dissertations  of  several  economists,  leave  me  no  doubt  as  to 
the  necessity  of  still  saying,  of  repeating  in  every  shape,  that  ma- 
chines have  never  been  the  true  and  permanent  cause  of  the  sufferings 
of  one  of  the  most  numerous  and  most  interesting  of  the  classes  of 
society;  that  their  destruction  would  aggravate  the  present  state  of 
things;  and  that  it  is  by  no  means  in  that  direction  that  a  remedy 
would  be  found  for  the  evils  which  I  warmly  compassionate. 


408  JAMES    WATT. 

derful  mechanical  combinations  that  we  are  accustomed  to 
admire  for  the  regularity  and  harmony  of  their  move- 
ments, for  the  power  and  delicacy  of  their  effects,  would 
be  instruments  of  injury ;  the  legislator  ought  to  pro- 
scribe them  with  a  just  and  implacable  rigour. 

Conscientious  opinions,  especially  when  they  are  con- 
nected with  praiseworthy  sentiments  of  philanthropy, 
have  a  claim  to  an  attentive  examination.  I  add,  that 
on  my  part  this  is  an  imperious  duty.  I  should  have 
neglected,  indeed,  the  argument  by  which  the  labours  of 
our  illustrious  academician  are  shown  to  be  most  worthy 
of  public  estimation,  if,  far  from  acceding  to  the  preju- 
dices of  certain  minds  against  the  improvement  of  ma- 
chines, I  did  not  point  out  such  works  to  the  attention  of 
well-meaning  men,  as  the  most  powerful,  the  most  direct, 
the  most  efficacious  means  of  rescuing  workmen  fi'om 
cruel  sufferings,  and  calling  them  to  partake  of  a  crowd 
of  benefits,  which  seemed  to  be  regarded  as  the  exclusive 
appanage  of  riches. 

When  we  have  to  select  one  of  two  diametrically  op- 
posite propositions  ;  when  the  one  being  true,  the  other 
must  be  false,  and  when  nothing  seems  at  first  sight  to  be 
able  to  dictate  a  rational  choice,  geometers  seize  on  these 
contrary  propositions  ;  they  follow  up  their  details  care- 
fully through  all  their  ramifications  ;  they  make  their 
last  logical  results  rise  up :  now  the  ill-stated  proposition, 
and  that  one  only,  seldom  fails  to  lead,  by  wire-drawing, 
to  some  results  that  a  clear  intellect  could  not  admit. 
Let  us  try  for  a  moment  the  method  of  examination  that 
Euclid  often  uses,  and  which  is  so  justly  designated  by 
the  epithet  of  mode  of  reducing  to  absurdity. 

The  adversaries  of  machines  would  wish  to  annihilate 
them,  or  at  least  to  restrain  their  propagation, — to  re- 


REDUCTIO    AD    ABSURDUM.  409 

serve,  say  they,  more  employment  for  the  workino-  classes. 
Let  us,  for  a  moment,  take  up  this  position,  and  the 
anathema  will  be  found  to  extend  far  beyond  machines 
properly  so  called. 

From  the  beginning  we  shall  be  led,  for  example,  to 
tax  our  ancestors  with  great  improvidence.  If  instead 
of  founding,  if  instead  of  persevering  in  extending  the 
city  of  Paris  on  the  two  banks  of  the  Seine,  they  had 
established  it  in  the  middle  of  the  plain  of  Villejuif,  for 
centuries  back  the  water-carriers  would  have  formed  the 
most  occupied,  the  most  numerous,  the  most  important 
portion  of  the  population.  Well,  Messrs.  Economists, 
set  to  work  in  favour  of  the  water-carriers.  To  make 
the  Seine  deviate  from  its  course  is  not  an  impossibility  ; 
propose  this  undertaking ;  open  a  subscription  immedi- 
ately to  leave  Paris  dry,  and  the  general  laugh  will  show 
you  that  the  rnode  of  reducing  to  absurdity  *  has  some 
good  in  it,  even  in  political  economy ;  and  in  their  plain 
sense,  the  workmen  themselves  will  tell  you  that  the 
river  has  created  the  immense  capital  in  which  such  re- 
sources are  found  ;  and  that,  without  it,  Paris  would  per- 
haps still  be  a  Villejuif. 

Good  Parisians  had  hitherto  congratulated  themselves 
on  the  vicinity  of  those  inexhaustible  quarries  where  suc- 
cessive generations  go  to  dig  out  materials  for  the  con- 
struction of  their  temples,  their  palaces,  their  private 
dwellings.  A  mere  illusion  !  The  new  political  economy 
will  prove  to  you  that  it  would  have  been  eminently 
advantageous  if  the  plaster,  the  freestone,  and  rubble  had 

*  This  "  m^thode  de  reduction  a  I'absurde  "  is  the  reductio  ad  ab- 
surf?i«»,  or  arguing  ca;  a^sarcZo,  of  logicians  and  mathematicians;  in 
which  the  truth  of  a  proposition  is  proved  by  showing  that  the  con- 
trary "is  unreasonable. —  Translator. 

SEC,    SEU.  18 


410  JAMES    WATT. 

been  found  only  near  Bourges  for  example.  On  this 
hypothesis,  compute  on  your  fingers  the  number  of  work- 
men that  would  have  been  required  to  bring  to  the  site 
of  the  capital  all  the  stone  that  during  five  centuries  has 
been  worked  up  by  architects,  and  you  will  find  a  truly 
prodigious  result :  and  however  little  the  new  ideas  may 
smile  upon  you,  yo«  may  go  into  ecstasies  at  your  ease 
on  the  happiness  that  such  a  state  of  things  would  have 
shed  on  the  proletaries. 

Let  us  venture  some  doubts,  although  I  know  very 
well  that  the  Vertots  of  our  day  perfectly  resemble  the 
Rhodian  historian,  when  their  seat  is  made,  (''  quand  leur 
siege  est  fait.") 

The  capital  of  a  powerful  kingdom,  not  very  distant 
from  France,  is  traversed  by  a  majestic  river,  which 
even  men-of-war  ascend. under  full  sail.  The  surround- 
ing country  is  furrowed  in  all  directions  by  canals  which 
carry  heavy  burdens  at  a  very  small  freightage.  A  regu- 
lar network  of  routes,  admirably  kept  up,  lead  to  all  the 
most  distant  parts  of  that  territory.  To  these  gifts  of 
nature  and  of  art,  this  capital,  which  of  course  every  one 
has  already  named,  unites  an  advantage  of  which  Paris 
is  deprived  ;  the  quarries  of  building-stone  are  not  at  its 
gates,  they  lie  at  a  distance.  There  then  the  Utopia  of 
the  new  economists  is  realized.  Will  they  not  now  count 
up  by  hundreds  of  thousands,  perhaps  by  millions,  the 
quarrymen,  the  boatmen,  the  carters,  the  labourers  in- 
cessantly employed,  digging  out,  carrying  away,  prepar- 
ing the  building-stone  for  the  construction  of  the  immense 
number  of  edifices  with  which  that  capital  is  annually 
enriched  ?  We  will  leave  them  to  count  at  their  ease. 
There  has  happened  in  that  city  what  would  have  hap- 
pened in  Paris  if  it  had  been  devoid  of  its  rich  quarries  ; 


UTILITY    OF    MACHINES.  411 

Stone  being  very  dear,  it  is  not  used ;  *  brick  is  the  gen- 
eral substitute. 

Millions  of  workmen  are  now  executing,  both  on  the 
surface  of  the  earth  and  in  its  bowels,  immense  works 
which  could  not  possibly  be  undertaken,  if  certain  ma- 
chines were  proscribed.  Two  or  three  examples  will 
suffice  to  render  this  truth  palpable. 

The  carrying  off  the  water  that  rises  daily  in  the  gal- 
leries of  the  Cornish  mines  alone,  requires  the  power  of 
50,000  horses,  or  of  300,000  men.  I  ask  you  whether 
the  pay  of  300,000  workmen  would  not  absorb  all  the 
benefit  of  the  undertaking  ? 

Does  the  question  of  the  expense  and  the  benefit 
appear  to  be  too  delicate  ?  Other  considerations  will 
lead  to  the  same  result. 

The  working  of  one  Cornish  mine  alone,  comprised 
under  the  name  of  the  Consolidated  Mines,  requires  a 
steam-engine  equal  to  upwards  of  three  hundred  horses 
constantly  in  harness,  and  each  twenty-four  hours  it 
realizes  the  work  of  one  thousand  horses.  Need  I  fear 
any  contradiction  if  I  assert  that  there  are  no  means  of 
making  upwards  of  three  hundred  horses,  or  two  thou- 
sand or  three  thousand  men,  labour  simultaneously  and 
to  good  purpose  around  the  confined  mouth  of  the  shaft 
of  a  mine  ?  To  proscribe  the  steam-engine  of  the  Con- 
solidated Mines  would  be  to  reduce  to  inaction  the  great 
number  of  workmen  that  the  engine  j-enders  it  possible 
to  employ  there  ;  it  would  be  the  same  as  declaring  that 
the  copper  and  tin  of  Cornwall  shall  remain  buried  there 
for  ever,  under  a  mass  of  earth,  of  rock,  and  of  water 
several  hundred  meters  in  thickness.    The  thesis  brought 

*  This  is  a  very  incon-ect  expression,  and  might  mislead  a  Parisian 
hadaud. —  Translator. 


412  JAMES    WATT. 

into  this  last  form  will  certainly  have  few  defenders; 
but  what  signifies  the  form  when  the  substance  is  evi- 
dently the  same  ? 

If  from  labours  that  require  an  immense  development 
of  power,  we  were  to  pass  on  to  the  examination  of  vari- 
ous industrial  products,  which,  from  the  dehcacy  of  their 
materials  and  the  regularity  of  their  forms,  have  been 
placed  among  the  wonders  of  art,  the  insufficiency,  the 
inferiority,  of  our  organs  compared  with  ingenious  me- 
chanical combinations,  would  equally  strike  all  minds. 
Where  is  there,  for  instance,  so  clever  a  spinner  as  to 
draw  a  thread  from  one  pound  of  cotton  wool  fifty-three 
leagues  long,  as  is  done  by  the  machine  called  the  mule- 
jemiy  ? 

I  am  not  ignorant  of  what  certain  moralists  have 
preached  on  the  inutiUty  of  muslins  and  laces  and  gossa- 
mer net,  in  the  weaving  of  which  this  fine  thread  is 
used ;  but  it  suffices  for  me  to  remark,  that  the  most 
perfect  mule-jenny  spins  under  the  constant  inspection 
of  a  great  many  workpeople ;  that  the  only  requisite  they 
care  for  is,  to  manufacture  goods  that  will  sell ;  in  short, 
that  if  luxury  is  an  evil,  a  vice,  or  even  a  crime,  it  is  the 
buyers  who  are  to  blame,  and  not  the  poor  proletaries, 
whose  existence,  I  believe,  would  be  very  uncertain  if 
they  themselves  endeavoured  to  manufacture  for  the 
ladies  woollen  stuffs  instead  of  fashionable  tulle. 

Now  let  us  quit  remarks  on  details,  and  dive  down  to 
the  very  bottom  of  the  question. 

Marcus  Aurelius  said:  "We  must  not  receive  the 
opinions  of  our  fathers  as  children  would,  for  the  mere 
reason  that  they  were  our  fathers'  opinions."  This 
maxim,  though  assuredly  a  very  just  one,  ought  not  to 
prevent  us  from  thinking,  or  at  least  from  presuming. 


UTILITY    OB'    MACHINES.  413 

that  those  ophiions  against  which  no  criticism  has  ever 
been  pronounced  from  the  commencement  of  societies, 
are  conformable  to  reason  and  to  general  advantage. 
Well,  on  the  question  so  much  debated,  relative  to  the 
utility  of  machines,  what  was  the  unanimous  opinion  of 
antiquity  ?  Its  ingenious  mythology  will  inform  us  ;  the 
founders  of  empires,  the  legislators,  the  conquerors  of 
tyrants  who  oppressed  their  country,  received  the  title  of 
demi-gods  only ;  but  it  was  among  the  gods  themselves 
that  they  placed  the  inventors  of  the  spade,  the  sickle, 
and  tlie  plough. 

I  already  hear  our  adversaries,  on  account  of  the 
extreme  simplicity  of  the  instruments  that  I  have  cited, 
boldly  refuse  them  the  name  of  machines,  unwilling  to 
regard  them  as  any  thing  but  tools  ;  and  ensconce  them- 
selves obstinately  behind  this  distinction. 

I  might  answer  that  such  a  distinction  is  puerile  ;  that 
it  would  be  impossible  to  say  precisely  where  the  tool 
ends  and  the  machine  begins  ;  but  it  is  better  worth 
remarking  that  in  the  pleadings  against  machines  noth- 
ing has  ever  been  said  of  their  greater  or  less  complica- 
tion. If  they  are  repudiated,  it  is  because  with  their  aid 
one  man  can  do  the  work  that  would  otherwise  require 
several  men ;  now  would  any  one  dare  to  maintain  that 
a  knife,  a  gimblet,  a  file,  a  saw,  do  not  confer  great  facil- 
ity of  operation  on  the  hand  that  uses  them ;  that  the 
hand  thus  strengthened  would  not  do  the  work  of  a  great 
many  hands  armed  only  with  their  nails  ? 

The  workmen,  seduced  by  the  detestable  theories  of 
some  of  their  pretended  friends,  did  not  stop  at  the 
sophisticated  distinction  between  tools  and  machines ; 
they  wandered  over  certain  counties  of  England,  in 
1830,  vociferating  the   cry  of  doivn  with  the  machines ! 


414  JAMES    WATT. 

Kigorous  logicians,  they  broke  in  the  farms,  the  sickle 
intended  to  reap  the  corn,  the  flail  that  was  to  beat  the 
corn,  the  sieve  by  the  aid  of  which  the  corn  is  winnowed. 
And,  in  fact,  are  not  the  sickle,  the  flail,  and  the  sieve 
means  for  shortening  labour  ?  The  spade,  the  hoe,  the 
plough,  the  seedsower,  could  not  find  grace  in  the  eyes 
of  this  blinded  horde  ;  and  if  any  thing  surprises  me,  it 
is  that  in  their  fury  they  spai-ed  the  horses,  a  sort  of 
machine  comparatively  cheap  to  keep,  and  each  of  which 
could  do  daily  as  much  work  as  six  or  seven  men. 

Political  economy  has  fortunately  obtained  a  place 
among  the  sciences  of  observation.  The  substitution  of 
machines  for  animated  beings  has  been  so  often  tried 
during  many  years  past,  that  people  cannot  hereafter  but 
perceive  the  general  results  amidst  some  accidental 
irregularities.     These  results  are  as  follows  : 

By  sparing  manual  labour,  machines  enable  us  to 
manufacture  at  a  cheaper  rate  ;  the  effect  of  this  cheap- 
ness in  an  increased  demand,  sueh  an  increased  demand 
(so  vivacious  is  our  desire  to  be  well  off)  that  notwith- 
standing the  most  inconceivable  lowering  of  price,  the 
money  value  of  the  totality  of  the  merchandise  produced, 
surpasses  each  year  what  it  was  before  the  improve- 
ment ;  the  number  of  workmen  employed  by  each  branch 
of  industry  increases  with  the  introduction  of  means  for 
manufacturing  expeditiously. 

This  last  result  is  exactly  contrary  to  what  is  wished 
for  by  those  who  hate  machines.  At  first  sight  it  may 
appear  paradoxical,  yet  we  shall  soon  see  it  proved  by 
a  rapid  examination  of  the  most  confirmed  industrial 
facts. 

When,  three  centuries  and  a  half  ago,  the  printing 
machine  was  invented,  copyists  used  to  furnish  books  to 


MANUFACTURE    OF    BOOKS.  415 

the  very  small  number  of  rich  men  who  could  indulge  in 
this  expensive  fancy.  One  of  these  copyists  being  able 
by  the  aid  of  the  new  proceeding  to  do  the  work  of  two 
hundred,  there  were  not  wanting  men  in  that  epoch  who 
dubbed  the  new  invention  as  infernal,  as  about  to  reduce 
to  inaction,  in  a  certain  rank  of  society,  nine  hundred 
and  ninety-five  men  out  of  one  thousand.  But  let  us 
now  place  the  real  result  by  the  side  of  the  sinister  pre- 
diction. 

Manuscript  books  were  very  little  in  demand ;  printed 
books,  on  the  contrary,  on  account  of  their  low  price, 
were  sought  after  with  the  most  lively  eagerness.  It 
was  found  necessary  incessantly  to  reproduce  the  Greek 
and  Roman  authors.  New  ideas,  new  opinions  occa- 
sioned a  multitude  of  new  books  to  arise  ;  some  of  eternal 
interest,  others  inspired  by  passing  events.  At  last  it 
was  calculated  that  in  London,  before  the  invention  of 
printing,  the  book  trade  employed  only  two  hundred 
men,  now  they  are  counted  by  twenty  thousand. 

And  how  much  more  would  it  be  if,  laying  aside  the  con- 
fined, and  I  might  say  material,  point  of  view  that  I  have 
had  to  select,  we  were  to  estimate  printing  by  its  moral 
and  intellectual  phases  ;  if  we  were  to  examine  the  influ- 
ence that  it  exerted  on  public  manners,  on  the  diffusion 
of  public  knowledge,  on  the  progress  of  human  reason  ; 
if  we  were  to  work  out  the  enumeration  of  the  many 
books  for  which  we  are  indebted  to  printing,  that  the 
copyists  would  certainly  have  disdained,  and  in  which 
genius  yet  goes  daily  gathering  the  elements  of  its  fruit- 
ful conceptions  ?  But  I  must  keep  in  mind  that  at 
present  we  have  only  to  treat  of  the  number  of  work- 
men employed  by  each  branch  of  industry. 

That  of  cotton  offers  even  more  demonstrative  results 


416  JAMES    WATT. 

than  is  done  by  printing.  When  Arkwright,  an  ingenious 
barber  of  Preston,  (who,  by  tlie  way,  left  each  of  his  cliil- 
dren  two  or  three  millions  of  francs  of  income,)  rendered 
it  both  useful  and  proiitable  to  substitute  revolving  cylin- 
ders for  the  fingers  of  the  women  who  used  to  spin,  the 
annual  product  of  the  cotton  manufacture  in  England  did 
not  exceed  50,000,000  francs  (2,000,000/.),  now  it  ex- 
ceeds 900,000,000  francs  (36,000,000/.).  In  the  county 
of  Lancaster  alone,  they  annually  deliver  to  the  calico 
manufacturers  a  quantity  of  yarn  that  21,000,000  clever 
spinners  could  not  accomplish  with  only  the  aid  of  the 
rock  and  spindle.  Moreover,  although  in  the  art  of  spin- 
ning mechanical  means  have  been  pushed,  we  may  say, 
to  their  utmost  degree  of  perfection,  1,500,000  people 
now  find  occupation  there,  where,  before  the  inventions 
of  Arkwright  and  of  Watt,  there  were  only  50,000.* 

A  certain  philosopher  exclaimed,  in  a  deep  fit  of  de- 
spondency, "Nothing  new  is  published  in  the  pi-esent 
day,  unless  we  call  new  that  which  has  been  forgotten." 
If  the  philosopher  alluded  only  to  errors  and  prejudices, 
he  spoke  truth.  Time  has  been  so  fruitful  in  this  line, 
that  no  one  can  any  more  claim  priority.  For  ex- 
ample, the  pretended  modern  philanthropists  have  not 
the  merit  (if  there  be  any  merit  in  it)  of  inventing  the 
systems  that  I  am  examining.  Rather  look  at  that  poor 
William  Lea  (Lee),  working  the  first  stocking-frame  in 
the  presence  of  James  I.  The  mechanism  apjjeared  ad- 
mirable ;  why  was  he  repulsed  ?     It  was  under  the  pre- 

*  Mr.  Edward  Baines,  author  of  a  much  esteemed  work  on  the  Brit- 
ish cotton  manufactures,  has  had  the  whimsical  curiosity  to  learn  what 
length  of  thread  is  annually  i;sed  in  weaving  the  cotton  manufactures. 
This  entire  length  he  finds  to  be  equal  to  ffty-one  times  the  distance  of 
the  sun  from  the  earth  !  (fifty-one  times  thirty-nine  millions  of  post 
leagues,  or  about  two  thousand  millions  of  si;ch  leagues.) 


MANUFACTURE    OF    STOCKINGS.  417 

text  that  the  working  class  would  suffer.  France  showed 
herself  equally  short-sighted  :  William  Lea  found  no  en- 
couragement there,  and  he  was  reduced  to  die  in  a  hos- 
pital ;  like  so  many  other  men  of  genius,  who  have  had 
the  misfortune  of  being  too  much  a-head  of  their  age  ! 

Besides  this,  we  should  be  very  much  mistaken  if  we 
supposed  the  body  of  knitters  very  numerous,  to  whom 
William  Lea  fell  a  victim.  In  1583,  it  was  only  people 
of  high  rank  and  fortune  who  wore  stockings.  The 
middle  class  substituted  for  this  portion  of  modern  dress 
narrow  stripes  of  variously  coloured  cloths.  The  rest  of 
the  population  (nine  hundred  and  ninety-nine  out  of  a 
thousand)  walked  bare-legged.  In  consequence  of  the  ex- 
tremely low  price  of  stockings  in  the  present  day,  there 
is  not  above  one  man  in  a  thousand  who  cannot  afford  to 
buy  them.  Hence  an  immense  number  of  workmen,  in 
every  part  of  the  world,  is  now  employed  in  this  branch 
of  manufacture.* 

If  it  be  deemed  necessary  I  will  add,  that  at  Stock- 
port, the  substitution  of  steam  power  for  manual  labour 
in  weaving  looms,  has  not  prevented  the  workmen  from 
increasing  by  one  third  in  a  few  years. 

We  must  now  deprive  our  adversaries  of  their  last  re- 

*  This  is  certainly  an  epochal  point  of  gi-eat  interest  in  domestic 
manufacture.  The  bandaged  stocking  is  of  a  very  remote  date,  and  is 
found  in  all  the  Saxon  figures  of  our  missals  and  monuments ;  it  was 
in  common  use  among  the  peasantry  of  Europe  even  during  the  fif- 
teenth century.  Henry  VIII.,  it  appears,  wore  silk  stockings,  and 
Queen  Elizabeth  refused  to  wear  any  others,  whence  they  came  into 
vogue.  These  seem  to  have  been  brought  from  abroad;  but  in  1564, 
William  Rider,  an  apprentice  on  London  Bridge,  borrowed  a  pair  of 
knit  worsted  stockings  from  Mantua,  took  the  hint,  and  made  a  pair 
exactly  like  them,  which  he  presented  to  the  Earl  of  Pembroke.  And 
these  are  the  first  pair  of  worsted  stockings  known  to  be  knit  in  Eng- 
land: the  prototype  of  millions  upon  millious. —  Translator. 
18* 


418  JAMES    AVATT. 

source  ;  we  must  not  leave  them  the  power  of  saying  that 
we  have  only  cited  old  branches  of  industry.  I  will, 
therefore,  now  remark  how  much  they  were,  not  long 
since,  deceived  in  their  lugubrious  forebodings  relative  to 
engraving  on  steel.  A  copper  plate,  they  said,  will  not 
give  above  two  thousand  impressions.  A  steel  plate,  by 
yielding  a  hundred  thousand  without  being  worn,  would 
replace  fifty  copper  plates.  Will  not  these  numbers  prove 
that  the  greater  part  of  the  former  engravers  (forty-nine 
out  of  fifty)  will  feel  obliged  to  abandon  their  profession, 
to  change  their  graver  for  the  trowel  or  the  hoe,  or  beg 
charity  in  the  public  streets  ? 

For  the  twentieth  time,  prophets  of  evil,  be  pleased 
not  to  forget  in  your  lucubrations,  the  principal  element 
of  the  problem  which  you  undertake  to  solve  !  Think 
of  the  insatiable  desire  to  be  well  off,  that  Nature  has 
implanted  in  the  human  heart ;  remember  that  one  wish 
is  no  sooner  satisfied,  than  it  immediately  gives  rise  to 
another  wish  ;  that  our  appetites  of  every  sort  increase 
with  the  cheapness  of  the  objects  adapted  for  their  indul- 
gence, and  to  a  degree  that  defies  the  creative  powers  of 
the  most  powerful  machines. 

But  to  return  to  tlie  engravings.  An  immense  major- 
ity of  the  public  did  without  them  when  they  were  dear ; 
their  price  decreases,  and  all  the  world  seeks  for  them. 
They  have  become  the  necessary  ornament  of  the  best 
books ;  to  middling  books  they  give  some  chance  of  sale. 
There  are  no  almanacs  even  now,  but  what  the  old  hid- 
eous figures  of  Nostradamus,  by  Matthew  Laensberg,  are 
replaced  by  picturesque  views  which,  in  a  few  seconds, 
transport  our  immovable  citizens  from  the  shores  of  the 
Ganges  to  those  of  the  Amazon,  from  the  Himalayas  to 
the  Cordilleras,  from  Pekin  to  New  York.     Look  also  at 


MACHINES  FAVOUR  POPULATION.        419 

those  engravers,  whose  ruin  was  so  piteously  announced 
to  us  ;  never  were  they  either  more  numerous  or  more 
occupied. 

I  am  going  to  bring  forward  some  irrefragable  facts. 
They  will  render  it  impossible,  I  think,  to  maintain  that 
among  the  inhabitants  of  this  earth,  such,  at  least,  as  Na- 
ture has  created,  the  use  of  machines  can  bring  on  the 
result  of  a  diminution  of  the  number  of  workmen  em- 
ployed in  each  sort  of  industry.  Other  customs,  other 
habits,  other  passions,  might,  perhaps,  have  led  to  an  en- 
tirely different  result ;  but  I  leave  such  a  text  to  those 
who  may  be  tempted  to  write  treatises  on  political  econ- 
omy for  the  use  of  the  inhabitants  of  the  Moon,  or  of 
Jupiter,  or  of  Saturn. 

Placed  in  a  much  more  confined  theatre,  I  ask  myself 
whether,  after  having  sapped  the  very  foundations  of  the 
system  maintained  by  the  adversaries  of  machines,  it  can 
be  still  requisite  to  cast  a  glance  at  some  criticisms  of  de- 
tail. Need  we  remark,  for  example,  that  the  poor's  rate, 
that  bleeding  wound  in  the  British  nation,  that  wound 
which  some  people  pretend  to  trace  to  the  abuse  of  ma- 
chines, dates  from  the  reign  of  Elizabeth,  from  a  period 
anterior  by  two  centuries  to  the  labours  of  Ai-kwrigiit 
and  of  Watt  ? 

You  will  at  least  acknowledge,  they  say  to  us,  that  the 
fire-machines,  the  mule-jennies,  that  the  machines  used 
for  carding,  for  printing,  &c.,  objects  of  your  predilection, 
have  not  prevented  pauperism  from  increasing  and  prop- 
agating itself.  This  fi-esh  avowal  will  cost  me  but  little. 
Did  any  one  recommend  machines  as  a  universal  panacea  ? 
"Was  it  ever  maintained  that  they  would  have  the  un- 
heard-of property  of  discarding  error  and  passion  from 
political  assemblies  ?  that  they  would  direct  the  counsel- 


420  JAMES    WATT. 

lors  of  pi'inces  to  the  paths  of  wisdom,  of  moderation,  of 
humanity  ?  Was  it  ever  pretended  that  they  would  turn 
Pitt  from  unceasingly  meddling  in  the  affairs  of  neigh- 
bouring countries  ?  fi'om  annually  raising  enemies  to 
France  in  every  part  of  Europe  ?  *  from  paying  them 
large  subsidies,  in  short,  from  loading  England  with  a 
debt  of  many  hundred  millions  ?  There,  there  is  the 
reason  why  the  poor's-rate  has  increased  so  fast,  and  so 
prodigiously.  Machines  have  not,  and  could  not,  pro- 
duce this  evil.  I  dare  even  assert  that  they  much  dimin- 
ish it ;  and  I  will  prove  it  in  a  few  words.  The  county 
of  Lancashire  carries  on  more  manufactures  than  any 
other  in  England.  It  is  there  that  we  find  the  cities 
of  Manchester,  Preston,  Bolton,  Warrington,  and  Liver- 
pool ;  it  is  in  that  county  that  machines  were  most  quickly 
and  most  generally  introduced.  Well,  let  us  distribute 
the  entire  annual  amount  of  the  poor-rates  of  Lancashire 
among  the  whole  of  its  population  ;  in  other  vs^ords,  let 
us  learn  what  would  be  the  quotient  for  each  individual ; 
and  we  shall  find  a  result  nearly  three  times  smaller  than 
the  mean  of  all  the  other  counties  !  You  see,  numbers 
are  pitiless  towards  the  inventors  of  theories. 

Moreover,  let  not  these  large  words  of  poor-rates  make 
us  believe,  on  the  faith  of  some  declaimers,  that  the  labour- 
ing classes  among  our  neighbours  are  entirely  devoid  of 

*  It  is  to  be  regretted  that  our  author  should  allow  his  prejudices, 
which  we  happen  personally  to  know  were  very  strong,  thus  again  to 
run  him  off  the  rail,  and  forget  his  promise  to  enter  upon  "  ce  mjet 
avec  la  ferrne  voluntu  d'etre  impartial."  While  he  assails  "  Pitt "  he  con- 
trives to  omit  the  provocation  and  necessity  of  the  case :  but  assuredly 
it  was  not  Pitt  who  broke  loose,  and  among  other  wild  and  unprece- 
dented phantasies,  invited  all  the  nations  of  Europe  to  demolish  their 
governments.  Yet  what  has  all  this  to  do  with  James  Watt  V —  Trans- 
lator. 


MACHINES    FAVOUR    POPULATION.  421 

resources  and  foresight.  A  work  of  recent  date  has  shown, 
that  in  England  alone  (Ireland  and  Scotland  being  thus 
left  aside),  the  capital  belonging  to  mere  workmen,  that 
has  been  deposited  in  the  savings'  banks,  amounts  to 
nearly  four  hundred  millions  of  francs  (16,000,000?.). 
The  verification  of  property  in  all  the  principal  towns 
is  not  less  instructive. 

One  principle  only  has  remained  uncontested,  amidst 
all  the  animated  debates  to  which  political  economy  has 
given  rise  :  and  this  is,  that  population  increases  with 
general  comfort,  and  that  it  diminishes  rapidly  in  times 
of  scarcity.*  Let  us  place  facts  by  the  side  of  the  prin- 
ciple. Whilst  the  mean  population  of  England  was 
increasing  during  the  last  thirty  years  50  per  cent., 
Nottingham  and  Birmingham,  two  of  the  most  indus- 
trial cities,  presented  a  still  larger  augmentation,  to  the 
amount  of  25  and  even  40  per  cent.f  Finally,  Man- 
chester and  Glasgow,  which  occupy  the  first  rank  in  the 
whole  British  empire,  from  the  number,  the  size,  and  the 
importance  of  the  machines  that  they  employ,  saw  their 
population,  in  the  same  period  of  the  last  thirty  years, 
increase  from  150  to  160  per  cent.  This  was  three  or 
four  times  more  than  in  the  agricultural  counties  and 
towns  not  possessing  manufactories. 

Such  numbers  speak  for  themselves.  No  sophistry, 
no  false  philanthropy,  no  efforts  of  eloquence,  can  resist 
them. 

*  Ireland  is  an  exception  to  this  rule,  the  cause  of  which  is  well 
known;  and  I  shall  have  occasion-to  recur  to  it. 

t  This  sentence  would  have  been  clearer,  had  the  author,  instead  of 
'■'■  accroissements  de  25  ei  de  iO  pour  100  plus  considerables  encore,'"  said 
75  and  even  90  per  cent. ;  because  he  means  25  added  to  the  above  50, 
and  40  added  to  the  50  per  cent., — since  he  gives  them  as  instances  of 
larger  augmentations. —  Translator. 


422  JAMES    WATT. 

Machines  have  given  rise  to  a  particulai*  kind  of  objec- 
tion, which  I  must  not  j^ass  over  in  silence.  At  the  time 
of  their  introduction,  at  the  time  when  they  begin  to 
take  the  place  of  manual  labour,  certain  classes  of  work- 
men suffer  from  the  change.  Their  honourable,  their 
laborious  industry,  is  almost  suddenly  annihilated.  Even 
those  who  under  the  old  system  were  the  cleverest,  being 
sometimes  devoid  of  the  qualities  required  in  the  new 
operations,  remain  unemployed.  They  seldom  succeed 
all  at  once  in  adapting  themselves  to  a  new  kind  of 
labour. 

These  reflections  are  just  and  true.  I  will  add  that 
the  bad  consequences  pointed  out  by  them  must  often 
recur :  some  caprice  in  the  fashions  even,  suffice  to  pro- 
duce deep  misery.  If  I  do  not  conclude  from  thence  that 
the  world  ought  to  remain  stationary,  God  forbid  that 
in  wishing  the  general  interests  of  society  to  advance,  I 
would  have  it  remain  deaf  to  the  individual  sufferings 
caused  by  this  temporary  advance  !  Authority,  always 
on  the  watch  relative  to  new  inventions,  seldom  fails  to 
catch  them  by  fiscal  measures.  Would  it  be  expecting 
too  much  from  it,  were  it  asked  to  allow  the  first  con- 
tributions levied  on  genius  to  be  devoted  to  opening  some 
special  workshops  where  the  artisans  who  had  been  sud- 
denly dispossessed  of  their  occupation  should,  for  a  time, 
find  employment  consonant  to  their  powers  and  their 
knowledge  ?  This  method  has  sometimes  been  found 
successful ;  it  would  then  only  remain  to  generalize  it. 
Humanity  makes  it  a  duty,  and  sound  policy  counsels  it ; 
besides  which,  some  terrible  events,  of  which  history  pre- 
serves the  recollection,  would  also  recommend  this  method 
on  the  part  of  economy. 

The  objections  of  theorists  who  feared  that  (he  progress 


CONSEQUENCES    OF    MACHINERY.  42.'^ 

of  mechanics  would  reduce  the  working  class  to  complete 
inaction,  have  been  followed  by  others  quite  of  a  different 
character,  and  on  which  it  appears  indispensable  to  dwell 
for  a  moment. 

By  suppressing  all  efforts  of  strength  in  manufactoi'ies, 
machines  allow  of  a  great  number  of  children  of  both 
sexes  being  called  in.  Some  industrial  and  some  avari- 
cious parents  often  abuse  this  power.  The  time  devoted 
to  work  is  most  unreasonably  long.  For  the  daily  pay 
of  eight  or  ten  centimes,  some  minds  are  devoted  to  eter- 
nal stupidity,  which  a  few  hours  of  study  would  have 
rendered  fruitful ;  limbs  are  condemned  to  be  rickety, 
that  required  open  air,  and  exercise  in  the  wholesome 
rays  of  the  sun  for  their  development. 

To  ask  a  legislator  to  put  an  end  to  this  hideous  ex- 
haustion of  the  poor  by  the  rich  ;  to  solicit  measures  for 
combating  the  demoralization  which  is  the  usual  conse- 
quence of  numerous  gatherings  of  young  work-people  ; 
to  try  to  introduce  and  distribute  certain  machines  among 
the  cottages,  so  that,  according  to  the  seasons,  agricultural 
labours  might  be  interspersed  with  the  industrial ; — this 
would  be  an  act  of  humanity,  an  act  of  patriotism ;  this 
would  show  a  knowledge  of  the  present  requirements  of 
the  working  classes.  But  to  persist  in  executing  labori- 
ously and  expensively,  by  hand,  works  that  machines  can 
perform  in  a  twinkling  and  at  a  low  price,  would  but  as- 
similate proletaries  to  brutes.  To  ask  daily  efforts  from 
them  which  ruin  their  health,  and  which  science  can  pro- 
cure a  hundredfold  by  the  action  of  wind,  of  water,  or  of 
steam,  would  be  going  in  the  contraiy  direction  to  the 
wislied-for  result  :  this  would  be  devoting  the  poor  to 
nudity  ;  reserving  exclusively  for  the  rich  a  host  of  enjoy- 
ments, which  at  present  are  shared  by  everybody :  this, 


424  JAMES    WATT. 

in  short,  would  be,  from  sheer  inconsiderateness,  going 
back  to  the  age  of  ignorance,  to  barbarity,  and  to  misery. 
It  is  time  to  quit  this  subject,  ahhough  I  am  far  from 
having  exhausted  it.  I  shall  not  assuredly  have  triumphed 
over  a  crowd  of  inveterate  and  systematic  prejudices  :  but 
I  may  hope,  at  least,  that  my  pleading  will  obtain  the 
concurrence  of  those  thousands  of  idlers  in  the  capital, 
whose  life  is  passed  in  proportioning  a  taste  for  pleasures 
with  their  bad  health.  In  a  few  years,  thanks  to  Watt's 
discoveries,  all  these  Sybarites,  incessantly  impelled  by 
steam  along  railways,  can  rapidly  visit  the  various  regions 
of  the  kingdom.  They  can  go  the  same  day  to  see  the 
fleet  get  under  weigh  at  Toulon  ;  breakfast  at  Marseilles 
on  the  succulent  roach  of  the  Mediterranean ;  at  noon 
plunge  their  enervated  limbs  in  the  mineral  waters  of 
Bagneres  ;  and  return  at  night,  by  way  of  Bordeaux, 
to  the  ball  or  the  opera  !  Do  you  doubt  this  ?  I  shall 
say  that  my  itinerary  only  supposes  a  rate  of  twenty-six 
leagues  per  hour ;  that  several  trials  of  steam  carriages 
have  realized  a  velocity  of  fifteen  leagues  ;  that  Mr.  Ste- 
phenson, in  short,  the  celebrated  engineer  of  Newcastle, 
offers  to  construct  steam-engines  two  and  a  half  times 
more  rapid :  engines  that  will  accomplish  forty  leagues 
per  hour ! 

PRESS   FOR   COPYING   LETTERS. HEATING  BY  STEAM. 

COMPOSITION    OF   WATER. BLEACHING   BY   THE    AID 

OF  CHLORINE. ESSAY  ON  THE  PHYSIOLOGICAL  EF- 
FECTS THAT  MAY  RESULT  FROM  BREATHING  VARI- 
OUS   GASES. 

When  Watt  went  to  reside  at  Soho,  Birmingham 
counted  Priestley  among  the  inhabitants  of  its  vicinity, — 
Priestley,  and  his  name  alone  says  all ;  Darwin  the  au- 


THE    LUNAR    SOCIETY.  425 

tlior  of  the  Zoonomia.  and  of  a,  celebrated  poem  entitled 
The  Loves  of  the  Plants ;  Withering,  a  distinguished 
physician  and  botanist ;  Keir,  a  chemist  well  known  by 
his  notes  to  his  translation  of  Macquer,  and  by  an  in- 
teresting memoir  on  the  ciystallization  of  glass  ;  Galton, 
author  of  an  elementary  treatise  on  Ornithology  ;  Edge- 
worth,  author  of  various  works  justly  appreciated,  and 
father  of  the  so  celebrated  Maria.  These  learned  men 
soon  became  friends  of  the  illustrious  mechanic,  and  most 
of  them  formed,  with  him  and  Boulton,  an  association 
c.alled  the  Lunar  Society.  Such  a  whimsical  appellation 
gave  rise  to  many  mistakes  :  it  only  meant  that  they  met 
on  the  evening  of  full  moon,  a  time  of  the  month  chosen 
by  preference,  in  order  that  the  members  might  see  their 
way  home. 

Each  sitting  of  the  Lunar  Society  was,  for  Watt,  a 
fresh  opportunity  for  showing  the  remarkable  fecundity 
of  invention  with  which  Nature  had  endowed  him. 
Darwin  said  one  day  to  his  companions,  "  I  have  im- 
agined a  certain  double  pen,  a  pen  with  two  beaks,  by 
the  aid  of  which  we  may  write  every  thing  in  duplicate ; 
and  thus  at  once  give  the  original  and  the  copy  of  a 
letter."  Watt  almost  immediately  replied  :  •'  I  hope  to 
find  a  better  solution  of  the  problem.  I  will  work  out 
my  ideas  to-night,  and  will  communicate  them  to  you  to- 
morrow." The  next  day  the  copying  press  was  invented, 
and  even  a  small  model  allowed  already  of  an  opinion 
being  formed  of  its  effects.  This  instrument,  so  useful 
and  so  generally  adopted  in  all  the  English  counting- 
houses,  has  recently  received  some  modifications,  an  hon- 
our claimed  by  many  workmen  ;  but  I  can  assert  that  the 
present  form  was  actually  described  and  drawn  in  1780, 
in  the  patent  of  our  associate. 


426  JAMES    WATT. 

"Warming  by  steam  was  more  recent  by  three  years. 
Watt  adopted  it  in  Jiis  own  house  in  1783.  We  must 
acknowledge  that  this  ingenious  method  is  found  indi- 
cated in  the  Philosophical  Transactions  for  the  year 
1745  by  Colonel  Cooke  ;  *  but  the  idea  passed  away 
unheeded.  At  all  events,  Watt  will  not  have  the  honour 
only  of  reviving  it :  he  was  the  first  to  apply  steam  ;  it 
was  his  calculations  on  the  extent  of  surface  requisite  for 
the  warming  of  halls  of  various  sizes,  that  in  the  begin- 
ning served  as  a  guide  to  the  greater  part  of  the  English 
engineers. 

If  Watt  had  only  produced,  in  the  course  of  his  long 
life,  the  separate  condenser  for  the  steam-engine,  the 
detent  for  regulating  the  steam,  and  the  afticulated 
parallelogram,  he  would  still  occupy  one  of  the  highest 
places  among  the  small  number  of  men  whose  life  marks 
an  epoch  in  the  history  of  the  world  ;  but  his  name  seems 
to  me  to  be  splendidly  connected  with  the  greatest  and 
the  most  important  discovery  in  modern  chemistry  :  the 
discovery  of  the  components  of  wafer.  My  assertion  may 
be  daring,  for  the  numerous  works  in  which  this  essential 
point  of  the  history  of  the  sciences  is  treated  ex  prof  esse, 
have  forgotten  Watt.  I  hope,  however  that  you  will 
follow  my  discussion  without  prejudice  ;  that  you  will 
not  allow  yourselves  to  be  deterred  from  the  examina- 

*  I  read  in  a  work  by  Mr.  Robert  Stuart  that  Sir  Hugh  Platte  had 
an  idea,  before  Colonel  Cooke,  of  the  possibility  of  applying  steam  to 
warming  dwellings.  In  the  Garden  of  Eden  by  that  author,  published 
in  1660,  something  is  said  to  that  effect  for  preserving  plants  through 
the  winter  in  the  green-house.  Sir  Hugh  Platte  proposes  placing  lids, 
made  of  tin  or  of  any  other  metal,  over  the  s.aucepans  in  which  the 
viands  are  being  cooked,  and  then  to  certain  openings  in  these  lids 
to  adapt  tubes,  by  which  the  heating  steam  may  be  led  wherever  it  is 
desired. 


THE    POUR    ELEMENTS.  427 

tion,  by  some  authorities  which  are  not  however  so  nu- 
merous as  might  be  supposed  ;  that  you  will  not  refuse 
to  remark  how  few  authors  in  the  present  day  refer  back 
to  original  sources  ;  how  disagreeable  they  find  it  to  dis- 
turb the  dust  of  libraries  ;  and,  on  the  contrary,  how  con- 
venient to  feed  on  the  erudition  of  other  people,  to  reduce 
the  composition  of  a  book  to  the  mere  work  of  editing. 
But  the  promise  that  I  hold  of  your  confidence  in  me, 
has  appeared  of  more  weight.  I  have  pressed  into  my 
service  a  number  of  printed  memoirs,  tlie  whole  of  a 
voluminous  authentic  correspondence  still  in  manuscript ; 
and  if  after  fifty  years  I  come  to  claim  for  Watt  an 
honour  that  has  been  inconsiderately  granted  to  one  of 
his  most  illustrious  countrymen,  it  is  because  it  has 
seemed  to  me  beneficial  to  show  that  in  the  heart  of 
academies,  truth  is  sure  to  shine  out  sooner  or  later,  and 
that  in  matters  of  discovery,  there  is  never  any  pre- 
scription. 

The  theory  of  the  four  pretended  elements,  fire,  air, 
water,  and  earth,  the  varied  combinations  of  which  were 
to  produce  all  known  bodies,  is  one  of  the  numerous  lega- 
cies that  have  come  down  to  us  from  the  brilliant  phil- 
osophy which,  through  several  centuries,  dazzled  and 
misled  some  of  the  noblest  intellects.  Van  Helmont 
was  the  first  who  shook,  though  slightly,  one  of  the  prin- 
ciples of  this  ancient  theorem,  by  pointing  out  to  the  at- 
tention of  chemists,  vai'ious  permanently  elastic  fluids, 
several  sorts  of  air,  that  he  called  gases,  the  properties 
of  wliich  differed  from  those  of  common  air,  from  those 
of  the  elemental  air.  Boyle's  and  Hooke's  experiments 
raised  more  serious  difficulties  still :  they  prove  that  com- 
mon air,  necessary  to  respiration  and  to  combustion,  un- 
dergoes remarkable  changes  in  the  course  of  tliose  two 


428  JAMES    WATT. 

phenomena,  and  exhibits  changes  of  properties  which 
imply  the  notion  of  composition.  The  numerous  obser- 
vations at  Hales ;  the  successive  discoveries  of  carbonic 
acid  by  Black,  of  hydrogen  by  Cavendish ;  of  nitrous 
acid,  of  oxygen,  of  muriatic  acid,  of  sulphurous  acid,  and 
of  ammonia  by  Priestley,  definitively  banished  the  old 
idea  of  there  being  a  unique  and  elementary  air ;  that 
being  among  the  almost  constantly  false  conceptions  haz- 
arded by  people,  who  have  the  audacity  to  think  them- 
selves called  upon,  not  to  discover,  but  to  guess  the  course 
of  nature. 

Amidst  so  many  remarkable  incidents,  water  had  still 
preserved  its  character  as  an  element.  The  year  177G  * 
was  at  last  signalized  by  one  of  those  observations  that 
were  to  lead  to  the  upsetting  of  this  general  belief.  It 
must  be  acknowledged  that  we  must  also  assign  the  same 
year  for  the  singular  efforts  made  by  the  chemists,  not  to 
surrender  to  the  natural  results  of  their  experiments. 
The  observation  of  which  I  wish  to  speak  belongs  to 
JMacquer. 

That  judicious  chemist  having  placed  a  white  porcelain 
saucer  over  the  flame  of  hydrogen  gas  which  was  burning 
tranquilly  out  of  the  mouth  of  a  bottle,  remarked  that 
this  flame  was  not  accompanied  by  any  smoke  properly 
so  called  ;  that  it  deposited  no  soot ;  that  the  part  of  the 
saucer  which  was  licked  by  the  flame  was,  on  the  contrary, 
evidently  covered  by  small  drops  of  a  fluid  resembling 
water,  and  which,  after  verification,  was  found  to  be  pure 
water.  This  was  certainly  a  singular  result.  Observe 
carefully,  it  was  in  the  midst  of  the  flame,  on  that  part  of 

*  It  was  in  this  year,  1776,  according  to  Priestley,  tliat  Volta  fired 
iifiaiTimable  air  by  tlie  electric  spark:  the  experiment  of  Macquer 
appears  to  have  been  made  two  years  afterwards. —  Translator. 


WATER    PROVED    A    COMPOUND.  429 

the  saucer  which  was  Uched  by  it,  as  Macquer  says,  that 
the  httle  drops  of  water  were  deposited.  The  chemist, 
however,  did  not  dwell  upon  this  fact ;  he  was  not  sur- 
prised at  what  it  contains  of  surprising :  he  simply  cites 
it  without  any  commentary ;  he  does  not  perceive  that 
he  was  touching  a  great  discovery  with  his  finger. 

Should  genius  then,  in  the  sciences  of  observation, 
be  reduced  to  the  faculty  of  asking,  at  appropriate  times, 
why'? 

The  physical  world  enrolls  volcanoes  that  have  never 
made  but  one  eruption.  It  is  the  same  in  the  intellectual 
world ;  for  there  are  men  who,  after  a  flash  of  genius, 
entirely  disappear  from  the  history  of  science.  Such 
was  Warltire,  whom  I  am  here  led  to  cite  by  the  chrono- 
logical order  of  dates  for  a  truly  remarkable  experiment. 
At  the  commencement  of  the  year  1781,  this  physicist 
imagined  that  an  electric  spark  could  not  pass  through 
certain  gaseous  mixtures  without  occasioning  some  de- 
cided changes  in  them.  So  novel  an  idea,  unsuggested 
by  any  previous  analogy,  but  of  which  such  happy  appli- 
cations have  since  been  made,  would  have  merited  for 
its  author,  I  think,  some  honourable  mention  on  the  part  of 
the  historians  of  science.  Warltire  was  wrong  as  to  the 
changes  that  electricity  would  create,  but  fortunately  for 
him  he  did  foresee  that  an  explosion  would  accompany 
them.  It  was  therefore  that  he  made  the  experiment  in 
a  metallic  vase,  having  enclosed  some  air  and  some  hy- 
drogen in  it. 

Cavendish  soon  repeated  Warltire's  experiment.  The 
positive  date  of  his  repetition  (I  call  thus  all  dates  re- 
sulting from  an  authentic  deposit,  or  an  academical  lec- 
ture, or  a  printed  paper)  is  anterior  to  the  month  of 
April  1783,  since  Priestley  cites  Cavendisli's  observations 


430  JAMES    WATT. 

in  a  memoir  of  the  21st  of  that  month.  The  citation 
besides  informs  us  only  of  one  circumstance  ;  it  is,  that 
Cavendish  had  obtained  water  by  the  detonation  of  a 
mixture  of  oxygen  and  hydrogen,  a  result  already  proved 
by  Warltire. 

In  his  April  memoir,  Priestley  added  a  remarkable 
circumstance  to  those  which  resulted  from  the  experi- 
ments of  his  predecessors,  for  he  proved  that  the  weight 
of  the  water  deposited  on  the  sides  of  the  vase  at  the 
moment  of  the  oxygen's  and  hydrogen's  detonation,  is 
the  sum  of  the  weight  of  both  the  gases. 

Watt,  to  whom  Priestley  communicated  this  important 
result,  immediately  saw  in  it,  with  the  penetration  of  a 
superior  mind,  that  water  is  not  a  simple  body. 

He  therefore  wrote  to  his  illustrious  friend :  "  What 
are  the  products  of  your  experiments,  wate?;  light,  and 
heat  f  Are  we  not  then  authorized  from  hence  to  con- 
clude that  water  is  a  union  of  oxyen  and  hydrogen  gas, 
deprived  of  a  portion  of  their  latent  or  elementary  heat ; 
that  oxygen  is  water  deprived  of  its  hydrogen  but  united 
to  latent  heat  and  light  ?  " 

"  If  light  be  only  a  modification  of  heat,  or  only  a  cir- 
cumstance attendant  on  its  manifestation,  or  a  component 
part  of  hydrogen,  oxygen  gas  must  be  water  deprived  of 
its  hydrogen,  but  united  to  some  latent  heat." 

This  passage,  so  clear,  so  neat,  so  methodical,  is  ex- 
tracted from  a  letter  by  Watt,  of  the  26th  of  April, 
1783.  The  letter  was  communicated  by  Priestley  to 
several  learned  men  in  London,  and  referred  immediately 
after  to  Sir  Joseph  Banks,  President  of  the  Royal  Society, 
to  be  read  at  a  meeting  of  that  learned  society.  Some 
circumstances,  which  I  suppress  because  they  are  irrele- 
vant to  our  present  purpose,  retarded  the  reading  by  a 


CAVENDISH    AND    LAVOISIER.  431 

year ;  but  the  letter  remained  in  the  archives  of  the 
Society.*  It  is  inserted  in  the  seventy-fourth  volume  of 
the  Philosophical  Transactions,  under  its  true  date  of 
the  26th  of  April,  1783.  It  is  found  there  inserted  in  a 
letter  from  Watt  to  De  Luc,  dated  2Gth  of  November, 
1783,  distinguished  by  inverted  commas,  applied  by  the 
Secretary  of  the  Royal  Society. 

I  do  not  ask  for  indulgence  on  this  profusion  of  details, 
it  will  be  perceived  that  a  minute  comparison  of  dates 
could  alone  bring  the  whole  truth  to  light ;  and  that  the 
subject  is  one  of  those  discoveries  that  do  most  honour  to 
the  human  mind. 

Among  the  pretenders  to  this  fruitful  discovery,  we 
are  now  going  to  see  arise  the  two  greatest  chemists 
boasted  of  by  France  and  England.  Everybody  must 
have  already  named  to  themselves  Lavoisier  and  Caven- 
dish. 

The  date  of  the  public  reading  of  the  memoir  in  which 
Lavoisier  detailed  his  experiments,  in  which  he  devel- 
oped his  views  on  the  production  of  water  by  the  com- 
bustion of  oxygen  and  hydrogen,  is  posterior  by  two 
months  to  Watt's  letter  (already  analyzed)  being  depos- 
ited in  the  archives  of  the  Royal  Society  of  London. 

The  celebrated  memoir  by  Cavendish,  entitled  Experi- 
ments on  Air,  is  more  recent  still ;  it  was  read  the  15th 
of  January,  1784.     It  might  excite  reasonable  surprise 

*  To  this  diffident  and  philosophical  document  we  refer  the  reader; 
in  it  Watt  states  that  he  feels  great  reluctance  to  lay  his  thoughts 
"before  the  public  in  their  present  indigested  state,  and  without 
having  been  able  to  bring  them  to  the  test  of  such  experiments  as 
would  confirm  or  refute  them."  M.  Arago,  in  rendering  portions  of 
the  paper,  resorts  to  the  exact  chemical  language  of  the  present  day; 
whence  he  uses  hydrog'ene  for  inflammable  air  and  phlogiston,  and 
oxygene  for  dephlogisticated  air. —  Translator. 


432  JAMES    "WATT. 

that  facts  so  well  authenticated  should  have  become  the 
subject  of  such  an  earnest  polemical  dispute,  if  I  did  not 
hasten  to  lay  before  you  a  circumstance  that  I  have  not 
mentioned  before.  Lavoisier  declared,  in  positive  terms, 
that  Blagden,  Secretary  of  the  Royal  Society,  of  London, 
was  present  at  his  first  experiments  on  the  24th  of  June, 
1783,  and  that  "  he  informed  him  that  Cavendish,  having 
already  tried  in  London  to  burn  hydrogen  gas  in  closed 
vessels,  had  obtained  a  very  sensible  quantity  of  water." 

Cavendish  also  I'epeated  in  his  memoir,  the  communi- 
cation made  by  Blagden  to  Lavoisier.  According  to  him, 
it  was  more  detailed  than  the  French  chemist  had  ac- 
knowledged. He  said,  that  the  information  included  the 
conclusion  to  which  the  experiments  led,  that  is  to  say, 
the  theory  of  water  being  a  compound. 

Blagden,  being  called  to  account,  wrote  in  the  Journal 
of  Creil,  in  1786,  to  confirm  the  assertion  made  by  Cav- 
endish. 

If  we  believe  this,  the  experiments  of  the  Academician 
of  Paris  would  not  have  been  more  than  a  simple  verifi- 
cation of  those  made  by  the  English  chemist.  He  assures 
us  that  he  announced  to  Lavoisier,  that  the  water  obtained 
in  London  was  pi'ecisely  equal  in  weight  to  the  sum  of 
the  weight  of  the  two  gases  that  had  been  burned.  And 
Blagden  finally  adds  :  "  Lavoisier  told  the  truth,  hut  not 
all  the  truth." 

Such  a  reproach  is  severe ;  but  if  it  were  well  founded, 
should  I  not  diminish  its  weight  very  much,  if  I  were  to 
show  that  excepting  "Watt,  all  those  whose  names  figure 
in  this  story  more  or  less  exposed  themselves  ? 

Priestley  details  some  experiments  as  if  they  were  his 
own,  and  it  results  from  them  that  the  water  engendered 
by  the  detonation  of  a  mixture  of  oxygen  and  hydrogen, 


CAVENDISH    AND    LAVOISIER.  433 

weighs  exactly  the  same  as  the  two  gases  burnt.  Some 
time  after,  Cavendish  claims  this  result  as  his  own,  and 
insinuates  that  he  had  communicated  it  verbally  to  the 
Birmingham  chemist. 

Cavendish  infers  from  this  similarity  of  weight,  that 
water  is  not  a  simple  body ;  yet  he  makes  no  mention  of 
a  memoir  deposited  in  the  archives  of  the  Royal  Soci.^ty, 
in  which  Watt  developed  the  same  theory.  It  is  true, 
that  at  the  day  of  publication  the  name  of  Watt  is  not 
forgotten  ;  but  it  was  not  in  the  archives  that  the  cele- 
brated engineer's  labours  could  be  seen  :  they  are  declared 
to  have  become  known,  by  a  recent  reading,  at  the  public 
meeting.  At  the  present  day,  however,  it  is  perfectly 
agreed  that  this  reading  followed,  by  several  months,* 
that  of  the  memoir  in  which  Cavendish  alludes  to  it. 

On  reaching  the  field  of  this  serious  discussion,  Blagden 
announces  his  firm  intention  to  elucidate  every  thing,  to 
correct  every  thing.  And  in  fact  he  did  not  draw  back 
from  any  accusation,  from  any  inquiry  into  dates,  as  long 
as  the  object  was  to  insure  to  his  patron  and  friend,  Cav- 
endish, a  priority  above  the  French  chemist.  But  as 
soon  as  his  explanations  concerned  two  of  his  country- 
men, they  became  vague  and  obscure.  He  says  :  "  In 
the  spring  of  1783,  Mr.  Cavendish  showed  us  that  he 
was  led  to  conclude  from  his  experiments,  that  water  is 
nothing  but  oxygen  deprived  of  its  phlogiston  (that  is  to 
say,  deprived  of  its  hydrogen).  About  the  same  time,  the 
news  reached  London,  that  Mr.  Watt,  of  Birmingham, 
had  been  led  by  some  observations,  to  a  similar  result." 
This  expression,  about  the  same  time,  to  speak  in  Mr. 

*  This  delay,  it  should  be  observed,  was  in  consequence  of  Watt's 
own  request ;  his  reason  for  so  doing  is  shown  in  the  note  to  page  432. 
—  Translator. 

SEC.    SER.  19 


434  JAMES    WATT. 

Blagden's  own  style,  would  not  be  all  the  truth.  About 
the  same  time  decides  nothing  :  questions  of  priority 
might  depend  on  weeks,  on  days,  on  hours,  on  minutes. 
To  be  clear  and  precise,  as  had  been  pi-omised,  he  should 
have  said  whether  the  verbal  communication  made  by 
Cavendish,  to  several  members  of  the  Royal  Society, 
preceded  or  followed  the  arrival  in  London  of  the  news 
of  Watt's  experiments.  Can  it  be  supposed  that  Blag- 
den  would  not  have  explained  himself  on  a  fact  of  this 
importance,  if  he  could  have  quoted  an  authentic  date  in 
favour  of  his  friend. 

To  render  the  complication  complete,  the  correctoi's  of 
the  press,  tlie  compositors,  the  printers,  of  the  Philosoph- 
ical Transactions,  all  took  part  in  this  affair.  Several 
dates  ai"e  incorrectly  given.  On  the  separate  copies  of 
his  memoir  Avhich  Cavendish  distributed  among  various 
learned  men,  I  perceive  an  error  of  a  whole  year.*  By 
a  sad  fatality,  for  it  is  a  real  misfortune  unwillingly  to 
give  rise  to  painful  and  undeserved  suspicions,  not  one 
of  these  numerous  errors  of  the  type  was  favourable  to 
Watt !  God  forbid  that  I  should  mean,  by  these  re- 
marks, to  criminate  the  literary  probity  of  the  illustrious 
philosophers  whose  names  I  have  cited  :  they  only  prove 
that  in  matters  of  discovery,  strict  justice  is  all  that  ought 

*  Our  author  must  have  been  excited  here,  for  he  thinks  that  not 
only  the  high-minded  Cavendish  and  Blagden,  but  even  the  printers 
of  the  papers,  were  in  a  conspiracy  against  Watt;  and,  though  he 
calls  God  to  witness  that  he  means  nothing  against  their  probity,  he 
makes  a  very  bold  insinuation  that  they  were  leagued  against  truth. 
The  separate  copies  of  Civendish's  paper,  pulled  off  for  private  dis- 
tribution, were  dated  1783  instead  of  1784;  as  soon  as  the  error  was 
discovered,  means  were  taken  to  correct  it.  Such  an  accidental  eiTor 
occurs  in  Watt's  own  communication  in  the  seventy- fourth  volume  of 
Transactions;  it  being  there  said  to  have  been  read  in  April,  1784, 
though  stated  to  have  been  written  in  November,  1784. —  TranslaUyr. 


RULE    FOR    PRIORITY    OF    CLAIM.  435 

to  be  expected  from  a  rival  or  competitor,  however  emi- 
nent his  reputation  may  already  be.  Cavendish  could 
scarcely  listen  to  people  on  business,  when  they  went  to 
consult  him  about  the  investment  of  his  twenty-five  or 
thirty  millions  (a  million  sterling  or  more)  ;  but  you 
now  know  whether  he  felt  equally  indifferent  about  ex- 
periments. It  would  not  be  requiring  too  much,  then,  if 
the  historians  of  science  were  not  to  receive,  as  available 
titles  to  property,  any  but  written  titles  ;  perhaps,  I  ought 
rather  to  say,  any  but  published  titles.  Then,  and  only 
then,  would  those  quarrels  end,  which  are  continually 
recommencing,  by  which  national  vanity  generally  suf- 
fers ;  then  the  name  of  Watt  Avould  resume  in  the  history 
of  chemistry  the  high  post  that  is  his  due. 

When  the  solution  of  a  question  of  priority,  like  the 
one  we  have  been  discussing,  is  founded  on  the  most 
attentive  examination  of  printed  memoirs,  and  on  a  minute 
comparison  of  dates,  it  assumes  the  character  of  a  real 
demonstration.  Still  I  feel  myself  bound  to  give  a  rapid 
glance  at  the  various  difficulties  to  which  some  veiy  good 
intellects  appear  to  me  to  have  attached  importance. 

How  can  it  be  admitted,  I  have  been  asked,  that  in  the 
midst  of  an  immense  whirlpool  of  commercial  affairs,  that 
preoccupied  by  a  multitude  of  lawsuits,  that  obliged  to 
provide  by  daily  inventions  against  the  difficulties  of  a 
rising  manufactory,  Watt  could  find  the  time  to  follow 
the  progress  of  chemistry  step  by  step,  to  make  fresh  ex- 
periments, to  propose  explanations  which  the  masters  of 
the  science  themselves  would  not  have  thought  of  ? 

To  this  difficulty  I  shall  make  a  short  but  conclusive 
reply :  I  hold  in  my  hands  the  copy  of  an  active  corre- 
spondence principally  relative  to  chemical  topics,  that 
Watt  kept  up  during  the  years  1782,  1783,  and  1784, 


436  JAMES    WATT. 

with  Priestley,  Black,  De  Luc,  the  engineer  Smeaton, 
Gilbert  Hamilton  (of  Glasgow),  and  Fry  (of  Bristol). 

The  following  is  an  objection  that  appears  more  spe- 
cious ;  it  arises  from  a  deep  knowledge  of  the  human 
heart. 

The  discovery  of  the  composition  of  water,  advancing 
step  by  step  with  the  admirable  inventions  that  are  united 
in  the  steam-engine,  can  we  suppose  that  Watt  would, 
from  inconsiderateness,  or  at  least  without  showing  any 
displeasure,  allow  himself  to  be  despoiled  of  the  lionour 
which  it  would  eternally  shed  on  his  name  ? 

This  reasoning  has  the  defect  of  erring  completely  at 
its  very  basis.  Watt  never  yielded  the  share  that  legiti- 
mately belonged  to  him  in  the  discovery  of  the  composi- 
tion of  water.  He  had  his  memoir  carefully  printed  in 
the  Philosophical  Transactions.  A  detailed  note  authen- 
tically proved  the  date  of  the  presentation  of  the  various 
paragraphs  of  that  writing.  What  could,  what  ought,  a 
philosopher  of  Watt's  character  to  do,  otherwise  than 
patiently  await  the  day  of  retribution  ?  However,  a 
piece  of  awkwardness  on  the  part  of  De  Luc  had  well 
nio'h  dragged  our  associate  from  his  forbearance.  The 
Genevese  physician,  after  having  warned  the  illustrious 
engineer  of  the  inexplicable  absence  of  his  name  from 
the  first  edition  of  Cavendish's  Memoir,  and  after  having 
described  this  omission  in  terms  which  the  high  renown 
of  both  parties  does  not  allow  me  to  repeat,  writes  to  his 
friend  :  "  I  should  almost  advise  you,  considering  your 
position,  to  extract  practical  results  from  your  discoveries, 
for  the  sake  of  your  purse." 

These  words  offended  Watt's  high  mind  ;  he  replied :, 
"  If  I  do  not  immediately  claim  my  rights,  you  must  im- 
pute it  to  an  indolence  of  disposition,  which  leads  me  to 


DISCOVERIES    BECOME    FAMILIAR.  437 

feel  it  easier  to  bear  with  injustice,  than  to  struggle  for 
redress.  And  as  to  considerations  of  pecuniary  interest, 
they  are  of  no  value  in  my  estimation.  Besides  which, 
,my  future  depends  on  the  encouragement  that  the  public 
may  be  inclined  to  grant  me,  and  not  at  all  on  that  of 
Mr.  Cavendish  or  of  his  friends." 

Ought  I  to  fear,  that  I  have  attached  too  much  im- 
portance to  the  theory  that  Watt  imagined  for  explain- 
ing Priestley's  experiments  ?  I  think  not.  Those  who 
would  refuse  a  rational  consent  to  this  theory,  because  it 
now  seems  the  inevitable  result  of  facts,  must  forget  that 
the  finest  discoveries  achieved  by  the  human  mind  have 
been,  above  all,  remarkable  for  their  simplicity.  What 
did  Newton  *  himself  do,  when,  repeating  an  experiment 
that  had  been  known  already  for  fifteen  centuries,  he  dis- 
covered white  light?  He  gave  so  natural  an  interpreta- 
tion of  this  experiment,  that  it  now  seems  impossible  to 
offer  any  other  ;  he  says — "  All  that  is  obtained,  by  any 
proceeding  whatever,  from  a  pencil  of  white  light,  must 
have  been  contained  in  it  in  a  state  of  mixture.  The 
glass  prism  possesses  no  creative  property.     If  the  paral- 

*  This  is  barely  in  point;  some  of  the  phenomena  of  colours  were 
certainly  known  before  the  advent  of  Newton,  but  that  jji'inceps liliihs- 
ophorum  formed  the  prismatic  spectrum  itself,  by  which  the  spaces 
occupied  by  the  successive  colours  were  accm-atel}-  defined,  the 
colours  submitted  to  a  similar  analysis,  and  the  white  light  re-formed; 
thus  ascertaining  and  proving  that  light,  instead  of  being  homoge- 
neous as  had  been  supposed,  was  actually  a  heterogeneous  mixture 
of  differently  refrangible  rays.  Nor  do  we  quite  quadrate  with  the 
lengthy  discussion  before  us,  since  we  do  not  consider  the  case — in  re 
the  beautiful  composition  of  water — to  be  conclusively  established. 
To  those  readers  who  are  interested  in  so  crucial  a  point  in  scientific 
history,  we  recommend  a  perusal  of  Vernon  Harcourt's  remarkable 
address  to  the  British  Association  at  Birmingham,  in  1839;  it  being 
alike  free  from  reckless  assertion,  and  that  hot  nationality  which 
warps  judgment. —  Translator. 


438  JAMES    WATT. 

lei  ray,  infinitely  diluted  with  the  solar  light  that  falls  on 
the  first  surface,  issues  from  the  second  surface,  diverging 
and  with  a  sensible  breadth,  it  is  because  the  glass  sepa- 
rates that  which,  in  the  white  pencil,  was  by  its  nature 
unequally  refrangible."  These  words  are  nothing  but  a 
literal  translation  of  the  known  experiment  of  the  pris- 
matic solar  spectrum.  This  translation,  however,  had 
escaped  an  Aristotle,  a  Descartes,  a  Robert  Ilooke. 

Without  departing  from  the  subject,  let  us  come  to 
some  arguments  which  will  lead  in  a  still  more  direct  line 
to  the  point.  The  theory  conceived  by  Watt  of  the  com- 
position of  water  reaches  London.  If  it  had  been  accord- 
ing to  the  ideas  of  those  times,  as  simple,  as  self-evident 
as  it  appears  to  us  now,  the  counsel  of  the  Royal  Society 
would  not  have  failed  to  adopt  it  :  but  4ts  strangeness 
made  them  doubt  the  correctness  of  Priestley's  experi- 
ments. They  went  so  far  as  to  laugh  at  it,  said  De  Luc, 
as  at  the  explanalion  of  the  golden  tooth. 

A  theory,  the  conception  of  which  did  not  present  any 
difficulty,  would  certainly  have  been  despised  by  Caven- 
dish. But  recollect  with  what  eagerness,  under  the  in- 
spiration of  that  man  of  genius,  Blagden  claimed  the 
priority  of  it  against  Lavoisier. 

Priestley,  to  whom  a  great  part  of  the  honour  of  Watt's 
discovery  belonged, — Priestley,  whose  affectionate  sen- 
timents for  the  celebrated  engineer  cannot  be  doubted, 
wrote  to  him,  under  date  of  the  29th  April,  1783, — 
"Look  with  surprise  and  indignation  at  the  drawing  of 
an  apparatus,  by  the  aid  of  which  I  have  irrevocably 
undermined  your  beautiful  hypothesis." 

In  conclusion,  an  hypothesis  at  which  they  laughed  in 
the  Royal  Society ;  which  made  Cavendish  emerge  from 
his  habitual  reserve  ;  which  Priestley,  laying  all  self-love 


PNEUMATIC    INSTITUTION.  439 

aside,  endeavoured  to  upset,  deserves  to  be  registered  in 
the  history  of  science  as  a  great  discovery,  whatever 
opinion  we  may  entertain  of  it  at  the  present  day,  owing 
to  knowledge  that  has  become  common.* 

The  art  of  bleaching  by  means  of  chlorine,  that  beau- 
tiful invention  of  BerthoUet's,  was  introduced  into  Eng- 
land by  James  Watt,  after  the  journey  he  made  to  Paris 
about  the  end  of  1786.  He  constructed  all  the  requisite 
apparatus,  directed  its  establishment,  presided  at  the  first 
trials ;  and  then  confided  to  Mr.  Macgregor,  his  father- 
in-law,  the  management  of  the  new  art.  Notwithstanding 
the  solicitations  of  the  illustrious  engineer,  our  celebrated 
countryman  had  obstinately  refused^  to  become  a  partner 
in  an  enterprise  which  offered  no  unfavourable  chance, 
and  the  profits  of  which,  it  seemed,  must  become  very 
great. 

Scarcely  had  they  discovered,  during  the  second  half 
of  the  last  century,  the  numerous  gaseous  substances, 
which  now  act  so  important  a  part  in  the  explanation  of 
chemical  phenomena,  when  they  thought  of  rendering 
them  useful  in  medicine.  Dr.  Beddoes  followed  up  this 
idea  with  sagacity  and  perseverance.  Private  subsci'ip- 
tions  even  enabled  him  to  establish  a  Pneumatic  Institu- 

*  Lord  Brougham  was  present  at  the  pubhc  meeting,  where,  hi  the 
name  of  the  Academy  of  Sciences  1  paid  tliis  tribute  of  gratitude  and 
admiration  to  Watt's  memory.  On  his  return  to  England  he  collected 
some  valuable  documents,  and  again  studied  the  historical  question  to 
which  I  have  devoted  so  much  space,  with  the  superiority  of  percep- 
tion which  is  familiar  to  him,  with  the  scrupulousness,  in  some  meas- 
ure justiciary,  which  might  be  expected  from  a  former  Lord  Chancellor 
of  Great  Britain.  I  owe  to  a  degree  of  kindness,  of  which  I  feel  the 
full  value,  the  advantage  of  being  able  to  offer  the  public  the  hitherto 
unpublished  researches  of  mj'  illustrious  co-academician.  See  the  end 
of  this  eloge. 

t  This  expression  is  correct,  however  fabulous  it  may  now  appear. 


440  JAMES    WATT. 

tion  at  Clifton,  near  Bristol,  where  the  therapeutic  proper- 
ties of  all  the  gases  were  to  be  carefully  studied.  The 
Pneumatic  Institution  had  for  some  time  the  advantage 
of  being  under  the  direction  of  the  young  Humphry 
Davy,  who  was  then  entering  on  his  scientific  career. 
It  could  boast  also  of  having  James  Watt  as  one  of  its 
founders.  The  celebrated  engineer  did  more  :  he  imag- 
ined, described  and  executed,  in  his  manufactory  at  Soho, 
the  apparatus  which  generated  the  gases  ;  and  he  admin- 
istered it  to  the  patients.  I  have  found  several  editions 
of  his  Memoir  treating  of  these  researches*  under  the 
several  dates  of  1794,  1795,  1796. 

Our  associate's  attention  was  attracted  to  this  subject, 
in  consequence  of  his  being  cruelly  deprived  of  several 
friends  and  relations  before  the  usual  age,  by  diseases  ol" 
the  chest.  It  was  chiefly  the  lesion  of  the  respiratoiy 
organs  that  Watt  thought  might  be  treated  by  the  aid  of 
the  specific  properties  of  the  new  gases.  He  also  ex- 
pected some  advantage  from  the  action  of  the  impalpable 
molecules,  of  iron,  and  of  zinc,  which  hydrogen  carries 
alono-  with  it  when  prepared  in  a  certain  way.  I  will 
finally  add,  that  among  the  numerous  medical  notes  pub- 
lished by  Dr.  Beddoes,  and  announcing  results  more  or 
less  decisive,  there  is  one  signed  John  Carmichael,  rela- 
tive to  the  radical  cure  of  haemoptysis  in  a  servant, 
Richard  Newberry,  who  was  made  at  certain  times  to 
breathe  a  mixture  of  steam  and  carbonic  acid  by  Watt 
himself.     Although  I  am  quite  aware  of  my  utter  incom- 

*  It  was  especially  the  illness  of  his  daughter,  and  the  delicate 
health  of  his  younger  son,  that  led  Watt  to  interest  himself  so  deeply 
on  this  head.  His  work  was  entitled  a  Description  of  a  Pneumatic 
Apixiratus,  ivith  Directions  for  procuring  the  Factitious  Airs. —  Trans- 
lator. 


WATT    IN    PRIVATE    LIFE.  441 

petence  on  such  a  subject,  may  I  not  be  permitted  to 
regret  that  a  treatment  which  counted  a  Watt  and  a  Jen- 
ner  among  its  adherents,  has  been  entirely  abandoned, 
ahhough  no  series  of  experiments  can  be  cited  in  mani- 
fest opposition  to  those  of  the  Pneumatic  Institution  at 
Clifton  ?  * 

WATT    IN    PRIVATE     LIFE. DETAILS     OF    EVENTS    AND 

OF     HIS      DISPOSITION. HIS      DEATH. NUMEROUS 

STATUES  ERECTED    TO    HIS    MEMORY. — REFLECTIONS. 

Watt  had  married,  in  1764,  his  cousin.  Miss  Miller. 
She  was  an  accomplished  person,  of  superior  mind,  and 
whose  never  failing  sweetness  and  cheerfulness  of  dispo- 
sition soon  raised  the  celebrated  engineer  from  the  indo- 
lence, the  melancholy  and  the  misanthropy  that  a  ner- 
vous illness  and  the  injustice  of  man  threatened  to  render 
fatal.  But  for  Miss  Miller,  Watt  would  probably  never 
have  made  his  beautiful  inventions  public.  Four  chil- 
dren, two  boys  and  two  girls,  were  the  fruit  of  this  mar- 
riage. Mrs.  Watt  died  at  the  birth  of  a  third  boy,  who 
did  not  survive.  Her  husband  was  then  busy  in  the 
north  of  Scotland,  with  the  plans  for  the  Caledonian 
Canal.  Why  should  I  not  be  permitted  to  transcribe 
here  with  all  their  originality  some  lines  from  the  journal 
to  which  he  committed  daily  his  most  private  thoughts, 
his  fears,  his  hopes  !  Why  should  I  not  show  him  to 
you,  after  his  misfortune,  stopping  on  the  sill  of  the  door 
of  his  house  where  his  siveet  welcomer  no  longer  awaited 

*  Twenty  years  before  the  establishment  of  the  Pneumatic  Insti- 
tution at  Bristol,  Watt  already  applied  his  chemical  and  minerological 
knowledge  to  improving  the  products  of  a  pottery  that  he  had  estab- 
lished at  Glasgow  together  with  some  friends,  and  of  which  he  con- 
tinued a  partner  to  the  end  of  his  life. 
19* 


442  JAMES    WATT. 

him  ;  unable  to  reenter  those  rooms,  where  he  was  no 
longer  to  find  the  comfort  of  his  life  !  Perliaps  so  true 
a  picture  of  deep  grief  would  silence  those  systematic 
spirits  who — without  pausing  at  the  thousands  of  strik- 
ing contrary  instances — deny  that  the  qualities  of  the 
heart  are  possessed  by  any  man  whose  intellect  has  been 
nurtured  with  the  fruitful,  the  sublime,  the  imperish- 
able truths  of  the  exact  sciences. 

After  remaining  for  some  years  a  widower,  Watt  had 
again  the  happiness  to  find  in  Miss  Mac  Grigor  a  com- 
panion worthy  of  him  by  the  variety  of  her  talents,  the 
soundness  of  her  judgment,  and  the  energy  of  her  char- 
acter.* 

At  the  expiration  of  the  patent  granted  him  by  Par- 
liament, Watt,  at  the  beginning  of  1800,  retired  entirely 
from  business. 

His  two  sons  succeeded  him.  Under  the  sensible 
direction  of  Mr.  Boulton  junior  and  the  two  young 
Messrs.  Watt  the  manufactory  at  Soho  prospered,  and 
exhibited  new  and  important  developments.  Even  now 
it  occupies  the  first  rank  in  England  among  the  estab- 
lishments for  constructing  large  machines.  The  second 
of  the  two  sons,  Gregory  Watt,  became  known  to  the 
world  in  a  brilliant  manner,  by  his  literary  compositions, 
and  by  his  geological  labours.  He  died  at  the  age  of 
twenty-seven,  in  1804,  of  a  disease  of  the  chest.  This 
sad  event  ovei*threw  the  illustrious  engineer.  The  ten- 
der attentions  of  his  family  and  of  his  friends  with  diffi- 
culty succeeded  in  restoring  some  degi*ee  of  calm  to  his 
broken    heart.       This    very   jusiifiable    grief  seems   to 

*  Mrs.  Watt  (Mac  Grigor)  expired  1832,  at  a  very  advanced  age. 
She  had  endured  the  grief  of  surviving  the  two  children  that  resulted 
from  her  marriage  with  Mr.  Watt. 


xni-:  GLASGOW  water-works.  443 

explain  the  almost  absolute  silence  which  Watt  main- 
tained during  the  several  latter  years  of  his  life.  I  am 
far  from  denying  that  it  was  without  influence  ;  but  what 
occasion  is  there  to  seek  for  extraordinary  causes,  when 
already,  under  date  of  1783,  we  read  in  a  letter  from 
Watt  to  his  friend  Dr.  Black  :  "  Recollect  well,  that  I 
have  no  desire  to  entertain  the  public  with  the  experi- 
ments which  I  have  made  ;  " — when  we  also  meet  else- 
where, these  very  singular  words  in  the  mouth  of  a  man 
who  has  filled  the  world  with  his  renown  :  "  I  know  only 
two  pleasures,  idleness  and  sleep."  This  sleep,  however, 
was  very  light  ;  and  let  us  add,  that  the  least  excitement 
sufficed  to  rouse  him  from  his  favourite  idleness.  All 
the  objects  that  Avere  presented  to  him  gradually  received 
from  him  a  mental  suggestion  of  change  of  form,  of 
nature,  or  of  construction,  which  would  have  rendered 
them  capable  of  important  applications.  These  concep- 
tions, for  want  of  opportunities  of  being  produced,  were 
lost  to  the  world.*  The  following  anecdote  will  explain 
my  ideas. 

A  company  at  Glasgow  had  erected  large  buildings 
and  powerful  engines  on  the  right  bank  of  the  Clyde, 
intended  to  carry  water  to  all  the  houses  in  the  town. 
When  this  work  was  completed,  they  perceived  that  there 
existed  on  the  opposite  shore  a  spring,  or  rather  a  natural 
filter,  which  gave  the  water  evidently  superior  qualities. 

*  There  can  be  no  doubt  that  Watt  was  deeply  affected  by  his  mel- 
ancholy bereavement;  but  his  mental  energy  was  never  impaired  by 
it,  nor  his  interest  in  science  and  literature  weakened.  Indeed  there 
seems  to  br  but  little  recollection  of  the  lengthy  silence  above  alluded 
to.  The  anecdote  which  follows  respecting  the  lobster's  tail,  which 
he  imitated  on  a  large  scale  by  a  sort  of  ball-and-socket  movement, 
shows  that  his  inventive  powers  were  still  bright  and  fertile  in  1811. 
—  Transla(m\ 


444  .TAJIKS    A7ATT. 

To  change  the  site  of  the  establishment,  could  not  even 
be  proposed  ;  they  therefore  thought  of  leading  a  fixed 
conduit-pipe  all  across  the  river,  along  the  bottom,  the 
mouth  of  which  should  always  be  in  the  midst  of  porta- 
ble water  ;  but  the  construction  of  the  wood-work  to 
support  such  a  pipe,  on  its  muddy,  changeable,  and  un- 
even bed,  always  covered  with  several  metres  of  water, 
seemed  to  require  too  heavy  an  outlay.  Watt  was  con- 
sulted. His  solution  was  all  ready ;  having  some  days 
before  seen  a  lobster  on  the  table,  he  sought  and  found 
how  mechanism  might,  with  the  aid  of  some  iron,  form  a 
series  of  articulations,  which  should  have  all  the  flexible 
mobility  of  the  tail  of  Crustacea  ;  he  therefore  proposed 
an  articulated  conduit-pipe,  susceptible  of  bending  itself 
to  all  the  present  and  future  inflections  of  the  bed  of  the 
river.  According  to  the  plans  and  designs  of  Watt, 
therefoi'e,  the  Glasgow  Company  ordered  this  iron  lob- 
ster-tail to  be  made,  sixty  centimetres  (nearly  two  feet) 
in  diameter,  and  above  three  hundred  metres  (1000 
feet,  English)  in  length ;  and  its  success  was  complete. 

Those  who  had  the  happiness  of  being  personally 
acquainted  with  him,  do  not  hesitate  to  assert  that,  in  his 
own  house,  the  qualities  of  his  heart  shone  even  above 
those  of  the  philosopher.  An  infantine  candour,  the 
greatest  simplicity  of  manners,  a  love  of  justice  carried 
beyond  every  scruple,  an  inexhaustible  benevolence, 
these  are  the  virtues  that  have  given  rise  to  indelible 
recollections  both  in  Scotland  and  England.  Watt, 
although  so  moderate  and  so  gentle,  became  irritated 
when  in  his  presence  an  invention  was  not  assigned  to 
its  true  author  ;  especially  when  any  low  flattei'er  wished 
to  enrich  him  at  other  men's  expense.  In  his  eyes, 
scientific  discoveries  were  the   highest  of  all  property. 


scott's  estimation  op  avatt.  445 

Whole  hours  of  discussion  did  not  seem  too  much  to  him, 
if  the  object  was  to  do  justice  to  diffident  inventors,  either 
robbed  hy  plagiarists,  or  only  forgotten  by  an  ungrateful 
public. 

Watt's  memory  might  be  cited  as  prodigious,  even 
by  the  side  of  all  that  is  related  of  this  faculty  in  some 
highly  endowed  men.  Its  extent,  however,  was  its  least 
merit ;  it  imbibed  all  that  was  of  any  value  ;  and  it  en- 
tirely rejected,  almost  instinctively,  the  superfluities  that 
it  would  have  been  useless  to  preserve. 

The  variety  of  knowledge  possessed  by  our  academi- 
cian would  be  truly  incredible,  if  not  attested  by  many 
eminent  men.  Lord  Jeffrey,  in  an  eloquent  biogi'aphical 
notice,  happily  characterized,  both  the  strong  and  subtle 
intelligence  of  his  friend,  when  he  compared  it  to  the 
elephant's  trunk,  so  wonderfully  organized,  that  the 
animal  uses  it  with  equal  facility  either  to  "  pick  up  a 
pin  "  or  "  to  rend  an  oak." 

Sir  Walter  Scott  speaks  of  his  countryman  in  the  fol- 
lowing terms,  in  the  preface  to  The  Monastery  : —  * 

"  It  was  only  once  my  fortune  to  meet  him,  whether  in  body  or  in 
spirit  it  matters  not.     There  were  assembled  about  half  a  score  of  our 

Northern  Lights Amidst  this   company  stood  Mr.  Watt,  the 

man  whose  genius  discovered  the  means  of  multiplying  our  national 
resources  to  a  degree  perhaps  even  beyond  his  own  stupendoxis  pow- 
ers of  calculation  and  combination ;  bringing  the  treasures  of  the 
abyss  to  the  summit  of  the  earth;  giving  the  feeble  arm  of  man  the 
momentum  of  an  Afrite ;  commanding  manufactures  to  rise,  as  the 
rod  of  the  prophet  produced  water  in  the  desert ;  affording  the  means 
of  dispensing  with  that  time  and  tide  which  wait  for  no  man ;  and  of 
sailing  without  that  wind  which  defied  the  commands  and  threats  of 
Xerxes  himself.  This  potent  commander  of  the  elements,  the  abridger 

*  We  have  thought  it  better  to  give  the  whole  passage  from  Sir 
Walter  Scott,  than  to  reproduce  it  from  our  author's  French;  nor 
liave  we  adopted  his  omissions. —  Translator. 


446  JAMKS    WATT. 

of  time  and  spaoe,  this  magician  whose  cloudy  machinery  has  pro- 
duced a  change  on  the  world,  the  effects  of  which,  extraordinary  as 
they  are,  are  perhaps  only  now  beginning  to  be  felt,  was  not  only  the 
profound  man  of  science,  the  most  successful  combiner  of  powers  and 
calculator  of  numbers  as  adapted  to  practical  purposes,  was  not  only 
one  of  the  most  generally  well  informed,  but  one  of  the  best  and  kind- 
est of  human  beings. 

"  There  he  stood,  surrounded  by  the  little  band  I  have  mentioned 
of  northern  literati,  men  not  less  tenacious,  generally  speaking,  of 
their  own  fame  and  their  own  opinions  than  the  National  Regiments 
are  supposed  to  be  jealous  of  the  high  character  which  they  have  won 
upon  service.  Methinks  I  yet  see  and  hear  what  I  shall  never  see  or 
hear  again.  In  his  eighty-fifth  {eighiy-tliird?)  year,  the  alert,  kind, 
benevolent,  old  man  had  his  attention  at  everj'  one's  question,  his 
information  at  every  one's  command. 

"  His  talents  and  fancy  overflowed  on  every  subject.  One  gentle- 
man was  a  deep  philologist — he  talked  with  him  on  the  origin  of  the 
alphabet  as  if  he  had  been  coeval  with  Cadmus;  another,  a  celebrated 
critic — you  would  have  said  the  old  man  had  studied  political  economy 
and  belles-lettres  all  his  life;  of  science  it  is  unnecessary  to  speak,  it 
was  his  own  distinguished  walk.  And  yet,  Captain  Clutterbuck, 
when  he  spoke  with  your  countryman,  Jedediah  Cleishbotham,  you 
would  have  sworn  he  had  been  coeval  with  Claver'se  and  Burley,  with 
the  persecutors  and  persecuted,  and  could  number  everj'  shot  the 
dragoons  had  fired  at  the  fugitive  covenanters.  In  fact  we  discovered 
that  no  novel  of  the  least  celebrity  escaped  his  perusal,  and  that  the 
gifted  man  of  science  was  as  much  addicted  to  the  productions  of  your 
native  country  (the  land  of  Utopia  aforesaid),  in  other  words,  as 
shameless  and  obstinate  a  peruser  of  novels  as  if  he  had  been  a  very 
milliner's  apprentice  of  eighteen." 

If  our  associate  had  wished  it,  he  could  also  have  made 
himself  a  name  among  novelists.  Among  his  intimate 
friends  he  seldom  failed  to  improve  on  the  terrible, 
moving,  or  burlesque  anecdotes  that  he  heard  related.  The 
minute  details  of  his  recitals,  the  proper  names  with 
which  he  strewed  them ;  the  technical  descriptions  he 
gave  of  the  castles,  the  country  houses,  the  forests,  the 
caverns,  to  which  the  sceng  was  successively  transferred, 
gave  to  these  impromptus  such  an  air  of  veracity,  that  one 


TALENT    FOR    RECITATION.  447 

could  not  entertain  the  slightest  sentiment  of  distrust. 
One  day  however,  Watt  was  at  a  loss  how  to  extricate 
his  characters  from  the  labyrinth  into  which  he  had  im- 
prudently thrown  them.  One  of  his  friends  perceived, 
by  the  uncommon  number  of  pinches  of  snuff  he  took, 
that  the  narrator  wished  thereby  to  excuse  frequent 
pauses,  and  gain  time  for  reflection.  He  therefore  ad- 
dressed this  indiscreet  question  to  him  :  "  Are  you  per- 
haps relating  to  us  a  story  of  your  own  ci'eation  ? " 
"  That  doubt  astonishes  me,"  wittily  replied  the  old  man  ; 
"  during  the  twenty  years  that  I  have  had  the  happiness 
of  passing  my  evenings  with  you,  I  have  done  nothing 
else  !  It  is  possible  that  they  really  wished  to  represent 
me  as  emulous  of  Robertson  or  of  Hume,  whilst  all  my 
ambition  was  limited  to  follow,  however  far  behind,  the 
steps  of  Princess  Scheherazade  in  the  Thousand  and 
One  Nights  !  " 

Each  year,  during  a  very  short  visit  to  London,  or  to 
other  towns  at  a  less  distance  from  Birmingham,  Watt 
examined  minutely  all  the  novelties  that  had  appeared 
since  his  preceding  visit.  I  do  not  except  even  the  sight 
of  the  industrious  fleas  or  the  puppet-shows  ;  for  the 
illustrious  engineer  went  to  them  with  all  the  delight  of 
a  school-boy.  While  perusing,  even  at  the  present  day, 
the  itinerary  of  these  annual  excursions,  we  should  find 
luminous  traces  of  Watt's  presence.  At  Manchester  for 
example,  we  should  see  the  hydraulic  ram  serving,  ac- 
cording to  his  own  proposition,  to  raise  the  water  of  con- 
densation from  a  steam-engine  up  to  the  reservoir  feeding 
the  caldron. 

Watt  generally  resided  on  an  estate  near  Soho  called 
Heathtield,  which  he  acquired  about  the  year  1790. 
The  filial  veneration  of  my  friend  Mr.  James  Watt,  for 


448  JAMES    WATT. 

every  thing  connected  with  his  father's  memory,  pro- 
curred  for  me,  in  1834,  the  satisfaction  of  finding  the 
library  and  the  furniture  at  Heathfield  in  the  same  state 
in  which  the  illustrious  engineer  left  them.  Another 
property  on  the  picturesque  banks  of  the  river  Wye,  in 
Wales,  offers  to  the  tourist  numerous  proofs  of  the  en- 
lightened taste  both  of  Watt  and  of  his  son,  by  the 
improvement  of  the  roads,  by  the  plantations,  and  by 
agricultural  labours  of  all  kinds. 

"Watt's  health  had  become  stronger  with  his  years. 
His  intellectual  faculties  continued  in  full  vigour  to  his 
last  moments.  He  thought  at  one  time  that  they  were 
declining,  and  adhering  to  the  thought  expressed  on  the 
seal  that  he  had  selected  (an  eye  surrounded  by  the  word 
Observare),  he  determined  to  clear  up  his  doubts  by  self- 
observation  ;  accordingly,  when  above  seventy,  we  see 
him  seeking  the  kind  of  study  to  which  he  should  best 
have  recourse  for  a  trial,  and  distressed  that  no  subject 
was  new  to  him.  He  recollects  at  last  that  there  is  an 
Anglo-Saxon  language,  that  it  is  a  difficult  language,  and 
the  Anglo-Saxon  becomes  the  desired  experimental  means, 
— the  facility  which  he  finds  in  rendering  himself  master 
of  it,  proves  to  him  how  unfounded  his  apprehensions 
were. 

Watt  devoted  his  last  days  to  the  construction  of  a 
machine  for  copying  promptly  either  statues  or  sculpture 
of  any  size  with  mathematical  fidelity.  This  machine, 
of  which  we  hope  the  arts  will  not  be  deprived,  must 
have  been  well  advanced.  Many  of  its  productions — 
already  very  satisfactory — may  be  seen  in  various  pri- 
vate collections  in  Scotland  and  in  England.  The  illus- 
trious engineer  had  presented  them  in  joke,  as  the  first 
essays  of  a  young  artist  entering  the  eighty-third  year  of 
his  age. 


STATUES    TO    WATT.  449 

It  was  not  permitted  to  our  associate  to  see  the  end  of 
this  eighty-third  year.  From  the  very  beginning  of  tlie 
summer  of  1819,  some  alarming  symptoms  defied  all  the 
powers  of  medicine.  Watt  himself  was  not  deceived. 
He  said  to  the  numerous  friends  who  visited  him — "  I 
am  moved  by  the  attachment  that  you  show  me,  I  hasten 
to  thank  you  for  it,  as  you  see  me  arrived  at  my  last  ill- 
ness." His  son  did  not  appear  to  him  sufficiently  re- 
signed ;  whereupon  he  each  day  sought  a  new  reason  by 
which  to  point  out  to  him  with  gentleness  and  tenderness, 
"  all  the  motives  of  consolation  that  he  might  derive  from 
the  circumstances  under  which  the  inevitable  event  was 
about  to  occur."  This  sad  event  did  in  fact  take  place 
on  the  2oth  of  August,  1819. 

Watt  was  buried  by  the  side  of  the  parish  cliurch  of 
Heathfield,  near  Birmingham,  in  the  county  of  Staftbrd. 
Mr.  James  Watt,  whose  distinguished  talents,  and  whose 
noble  sentiments  delighted  his  father's  heart  for  neai'ly 
twenty-five  years,  erected  a  splendid  Gothic  monument 
to  him,  and  it  now  greatly  adorns  Handsworth  Church.* 
In  the  centre  there  stands  an  admirable  statue  by 
Chantrey,  the  exact  representation  of  the  old  man's 
noble  features. 

A  second  statue,  also  of  marble,  from  the  hands  of  the 
same  sculptor,  has  been  placed  by  filial  piety  in  one  of 
the  halls  of  the  brilliant  university  where,  during  his 
youth,  the  then  unknown  artist,  though  harassed  by  the 
corporation,  received  such  flattering  and  well-deserved 
encouragement.     Isor  has  Greenock  forgotten  that  Watt 

*  To  a  general  reader  this  paragraph  might  convey  an  ambiguity; 
Watt  died  in  his  house  at  Heathfield,  at  the  age  of  eighty-three  years 
and  seven  months ;  and  his  remains  are  deposited  in  the  chancel  of 
the  adjoining  parochial  church  of  Handsworth,  near  those  of  his  ex- 
cellent friend  Miss  Boulton. —  Translatm-. 


450  JAMES    WATT. 

was  born  there.  The  inhabitants  have  subscribed  for  a 
statue  of  the  iUustrious  mechanic,  to  be  placed  in  a  fine 
library,  built  on  a  piece  of  ground  generously  given  by 
Sir  Michael  Shaw  Stewart ;  and  there  will  be  gathered 
the  books  that  the  town  possessed,  and  the  collection  of 
scientific  works  that  Watt  had  presented  to  the  towa 
during  his  life.  This  building  has  already  cost  3500^. 
sterling  (upwards  of  87,000  frs.  of  our  money),  a  con- 
siderable expense  for  which  the  liberality  of  Mr.  Watt, 
Junior,  has  provided.  A  grand  colossal  statue  in  bronze, 
on  a  beautiful  granite  base,  now  adorns  one  of  the  angles 
of  George's  Square,  at  Glasgow  ;  proving  to  all  beholders, 
how  much  that  capital  of  Scotch  industry  prides  itself  in 
having  been  the  cradle  of  Watt's  discoveries.  Finally,* 
the  gates  of  Westminster  Abbey  opened  at  the  imposing 
voice  of  a  host  of  subscribers  ;  and  a  colossal  statue  of 
our  co-academician,  of  Carrara  marble,  a  masterpiece  of 
Chantrey's,  the  pedestal  bearing  an  inscription  by  Lord 
Brougham,  has  become  within  these  few  years  one  of  the 
principal  ornaments  of  the  English  Pantheon.  Doubt- 
less a  little  coquetry  was  necessary  to  bring  together  the 
illustrious  names  of  Watt,  Chantrey,  and  Brougham  on 
the  same  monument ;  but  I  can  see  nothing  to  blame  in 
it :  glory  to  the  people  who  thus  seize  every  opportunity 
of  honouring  their  great  men  ! 

This  inscription  by  Lord  Brougham,  put  on  the 
pedestal  of  the  statue  of  our  confrere,  appears  to  us  to 
be  worthy  of  a  place  in  these  pages,  devoted  to  the  mem- 
ory of  one  of  the  greatest  geniuses  that  ever  illustrated 
science  and  industry  ;  we  will  reproduce  it  then  literally, 
a  translation  shall  follow  : — 

*  Two  years  ago  a  statue  of  Watt  was  erected  in  Edinburgh. — 
Translator. 


LORD    brougham's    INSCRIPTION.  451 

NOT  TO  PERPETUATE  A  NAME 

WHICH  MUST  ENDURE  WHILE  THE  PEACEFUL  ARTS  FLOURISH, 

BUT  TO   SHOW 

THAT  MANKIND  HAVE  LEARNT  TO  HONOUR  THOSE 

WHO  DESERVE  THEIR  GRATITUDE, 

THE  KING, 

HIS  MINISTERS,  AND  MANY  OF  THE  NOBLES 

AND    COMMONERS  OF  THE  REALM, 

RAISED  THIS  MONUMENT  TO 

JAMES  WATT, 

WHO  DIRECTING  THE  FORCE  OF  AN  ORIGINAL  GENIUS 

EARLY  EXERCISED  IN  PHILOSOPHIC  RESEARCH, 

TO  THE  IMPROVEMENT  OF 

THE  STEAM-ENGINE, 

ENLARGED  THE  RESOURCES  OF  HIS  COUNTRY, 

INCREASED  THE  POWER  OF  MAN, 

AND  ROSE  TO  AN  EMINENT  PLACE 

AMONG  THE  MOST  ILLUSTRIOUS  FOLLOWERS  OF  SCIENCE 

AND  THE  REAL  BENEFACTORS  OF  THE  WORLD. 

BORN  AT  GREENOCK,  MDCCXXXVI. 

DIED  AT  HEATHFIELD,  IN  STAFFORDSHIRE,  MDCCCXIX.* 

There  are,  actually  counted,  five  large  statues  erected 
in  a  slioz't  time  to  the  honour  of  "Watt.  Must  we  ac- 
knowledge it  ? — this  homage  of  filial  piety,  of  public 
gratitude,  has  excited  the  ill-humour  of  some  narrow 
minds,  who,  remaining  stationary  themselves,  think  they 
can  arrest  the  march  of  centuries.  If  we  believe  them, 
some  military  men,  some  magistrates,  some  ministers  (I 
must  confess  they  have  not  dared  to  say  all  the  ministers), 
would  have  a  right  to  statues.  I  know  not  whether 
Homer,  Aristotle,  Descartes,  Newton  would  appear  to 
these  new  Aristarchi  deserving  of  a  bust ;  assuredly  they 
would  refuse  the  most  unassuming  medal  to  the  Papins, 
the  Vaucansons,  the  Watts,  the  Arkwrights,  and  other 
mechanics,   unknown,  perhaps,  in  a  certain  world,   but 

*  The  French  trauslation,  for  obvious  reasons,  is  omitted. —  Trans- 
lator. 


452  JAMES    WATT. 

whose  renown  will  go  on  increasing  from  age  to  age  with 
the  progress  of  knowledge.  When  such  heresies  are 
brought  forward  in  open  daylight,  we  ought  not  to  dis- 
dain combating  them.  It  is  not  without  reason  that  the 
public  has  been  called  a  sponge  of  prejudices  ;  now  pre- 
judices are  like  noxious  weeds,  the  slightest  effort  suffices 
to  extirpate  them  on  their  first  appearance  ;  but,  on  the 
other  hand,  they  resist  if  they  are  allowed  time  to  grow, 
to  expand,  to  seize  by  their  numerous  organs  all  that  is 
suited  to  their  nature. 

If  this  discussion  should  wound  the  self-love  of  some 
people,  I  must  remark  that  it  has  been  provoked.  Have 
the  learned  men  of  our  own  times  uttered  complaints  at 
not  seeing  any  of  the  great  authors,  whose  inheritance 
they  cultivate,  figure  in  those  long  ranges  of  colossal 
statues,  which  authority  pompously  raises  on  our  bridges 
and  in  our  public  squares  ?  Do  they  not  know  that 
their  monuments  are  fragile,  that  storms  upset  and  de- 
stroy them,  that  frost  suffices  to  spoil  their  outlines,  and 
to  reduce  them  to  amorphous  blocks  ? 

Their  sculptui'e  and  their  painting  is  the  press.  Thanks 
to  that  admirable  invention,  when  the  works  which  science 
or  imagination  produces  possess  real  merit,  they  may  defy 
time  and  political  revolutions.  Neither  the  exigencies  of 
the  Exchequer,  nor  the  inquietudes  and  terrors  of  des- 
pots, could  prevent  those  productions  from  penetrating 
beyond  the  best-guarded  frontiers.  A  thousand  ships 
will  carry  them,  in  various  shapes,  from  one  hemisphere 
to  the  other.  They  will  be  read  in  Iceland  and  in  Van 
Diemen's  Land  at  the  same  time.  They  will  be  read  at 
evening  meetings  in  the  humble  cottage,  they  will  be  read 
in  brilliant  assemblies  in  palaces.  The  author,  the  artist, 
ihe  engineer  are  known,  appreciated,  by  the  whole  world, 


LITERARY    MERIT    DURABLE.  453 

by  that  which  there  is  in  man  of  most  noble,  of  most 
elevated  :  by  the  soul,  by  the  thoughts,  by  the  intellect. 
How  foolish  must  that  man  be  who,  placed  on  such  a 
theatre,  should  be  detected  in  wishing  that  his  lineaments 
were  preserved  by  the  chisel  of  a  David,*  to  be  some  day 
exposed  to  the  glances  of  idlers  taking  their  walk.  Such 
honours,  I  repeat  it,  need  not  be  envied  by  the  learned 
man,  by  the  author,  or  by  the  artist ;  but  they  ought  not, 
on  any  account,  to  allow  themselves  to  be  declared  un- 
worthy of  them.  Such,  at  least,  have  been  the  thoughts 
that  lead  me  to  submit  the  following  discussion  to  your 
judgment- 
Is  it  not  a  truly  strange  circumstance,  that  these  vain 
pretensions  that  I  am  combating  should  have  been  raised 
merely  on  account  of  these  five  statues,  not  one  of  which 
cost  a  single  obolus  to  the  public  treasury  ?  Far  from 
me,  however,  to  take  advantage  of  this  inconsiderateness. 
I  pi-efer  taking  the  question  in  a  more  general  point 
of  view,  such  as  it  was  laid  down  :  the  pretended  pre- 
eminence of  arms  over  letters,  over  science,  over  art ;  for 
we  must  not  deceive  ourselves — if  magistrates  and  ad- 
ministrators have  been  mentioned  together  with  military 
men,  it  was  only  as  a  passport. 

The  shortness  of  the  time  allowed  me  for  this  discus- 

*  It  is  uncertain  whether  the  noted  Jacques  Louis  David,  or  Pierre 
Jean  David  is  here  meant;  for  though  the  former  is  generally  known 
as  a  painter  only,  he  proposed  to  construct  a  huge  colossus  in  honour 
of  the  people,  out  of  the  ruins  of  royal  statues;  and  of  this  he  made  a 
model.  But  we  could  have  wished  that  our  author's  taste  had  pre- 
vented his  intruding  the  truisms  in  this  and  m  the  tirade  which  fol- 
lows; at  least,  the  biography  of  the  enriched  and  greatly  honoured 
Watt  hardly  appears  to  be  a  fit  peg  whereon  to  hang  so  laboured  a 
declamation.  Even  now,  one  of  the  finest  line-of-battle  ships  in  the 
British  fleet  is  the  James  Watt;  still,  we  admit,  the  best  records  of 
an  eminent  man  are  certainly  his  works. —  Translator. 


454  JAMES    WATT. 

sion,  imposes  on  me  the  duty  of  being  methodical.  In 
order  that  my  sentiments  may  not  be  mistaken,  I  will  at 
once  declare  aloud  that  independence,  that  national  lib- 
erty, are  in  my  opinion  the  greatest  possible  good  ;  that 
to  defend  them  against  foreigners,  or  against  internal 
enemies,  is  our  first  duty  ;  and  that  to  have  defended 
them  at  the  cost  of  our  blood,  is  the  highest  title  to  pub- 
lic gratitude.  Raise,  raise  splendid  monuments  to  the 
memory  of  the  soldiers  who  fell  on  the  glorious  ramparts 
of  Mayence,  on  the  immortal  fields  of  Zurich,  of  Marengo, 
and  certainly  my  offering  shall  not  be  waited  for ;  but  do 
not  require  me  to  do  violence  to  my  reason,  to  the  senti- 
ments that  Nature  has  implanted  in  the  human  heart ;  do 
not  hope  that  I  will  ever  consent  to  place  all  military 
services  on  the  same  level. 

What  Frenchman  possessed  of  a  heart,  even  in  the 
reign  of  Louis  XIV.,  would  have  sought  for  an  example 
of  courage  either  among  the  scenes  of  cruelty  in  the 
Dragonnades,  or  among  the  whirlwinds  of  flame  that 
devoured  the  towns,  the  villages,  and  the  rich  country 
of  the  Palatinate  ? 

Not  long  since,  after  a  thousand  prodigies  of  patience, 
of  cleverness,  of  bravery,  our  valiant  soldiers  penetrated 
into  the  half-destroyed  Saragossa,  and  reached  the  door 
of  a  church  where  the  preacher  was  still  making  the  ears 
of  the  resigned  crowd  ring  w^ith  these  magnificent  words : 
"  Spaniards,  I  am  going  to  celebrate  your  funerals  !  "  I 
know  not,  but  I  think  that  at  such  a  moment  the  true 
friends  of  our  national  glory,  comparing  the  various 
merits  of  the  conquerors  and  the  vanquished,  would 
willingly  perhaps  have  inverted  the  address  ! 

But  I  consent  to  your  laying  aside  the  question  of 
morality.     Submit  the  personal  claims  of  some  gainers 


HEROIC    ELOQUENCE.  455 

of  battles  to  the  crucible  of  a  conscientious  analysis  ; 
believe  me,  that  even  if  you  make  an  equitable  partition 
by  chance  (a  sort  of  ally  ior  whom  one  always  makes 
allowance,  as  being  dumb),  many  pretended  heroes  will 
appear  to  you  very  unworthy  of  that  pompous  title. 

If  it  were  found  requisite,  I  would  not  recoil  from 
a  detailed  examination  ;  I,  who  in  a  purely  academic 
career,  can  have  had  but  little  opportunity  of  collecting 
correct  documents  on  such  a  subject, — I  could,  for  exam- 
p\e,  cite  in  our  own  annals  a  recent  battle,  a  battle  gained, 
the  official  report  of  which  describes  it  as  having  been 
foreseen  and  calmly  prepared,  with  the  most  consummate 
ability ;  but  which,  in  reality,  was  the  result  of  a  sudden 
rush  on  the  part  of  the  soldiers,  without  any  order  from 
the  Commander-in-Chief  to  whom  the  honour  was  as- 
signed, without  his  having  been  there,  without  his  having 
known  of  it  ! 

To  escape  from  the  commonplace  reproach  of  incom- 
petence, I  will  call  on  some  military  men  themselves  to 
aid  in  supporting  the  philosophic  thesis  which  I  maintain. 
It  will  be  seen  what  enthusiastic  and  enlightened  appre- 
ciators  they  were  of  intellectual  labours  ;  it  will  be  seen 
that  in  their  inner  mind,  these  never  held  a  second  rank. 
Obliged  to  restrict  myself,  I  will  try  to  make  high  re- 
nown supply  the  deficiency  of  number  and  novelty  :  I 
will  cite  Alexander,  Pompey,  Cassar,  and  Napoleon  ! 

The  Macedonian  conqueror's  admiration  of  Homer  is 
historical.  Aristotle  at  his  desire  undertook  the  task  of 
revising  the  text  of  the  Iliad.  That  corrected  copy  be- 
came a  cherished  book  ;  and  when,  in  the  centre  of  Asia, 
amidst  the  spoils  of  Darius,  a  magnificent  casket  was 
found,  enriched  with  gold,  pearls,  and  precious  stones, 
which  seemed  to  excite  the  covetousness  of  his  highest 


456  JAMES    WATT. 

officers,  the  conqueror  of  Arbela  exclaimed :  "  Let  that 
be  reserved  for  me  ;  it  shall  contain  my  Homer.  It  is 
the  best  and  most  faithful  counsellor  I  have  in  my  mili- 
tary affairs.  Besides,  it  is  but  just  that  the  richest  pro- 
duction of  art  should  preserve  the  most  precious  work  of 
the  human  mind." 

The  sacking  of  Thebes  had  already  shown,  still  more 
clearly,  the  unlimited  respect  and  admiration  that  Alex- 
ander entertained  for  letters.  Only  one  family  out  of 
that  populous  city  escaped  death  and  slavery  :  this  was 
the  family  of  Pindar.  Only  one  house  remained  intact 
amidst  the  ruined  temples,  palaces,  and  private  dwellings  : 
this  was  the  house  where  Pindar  was  born,  not  Epami- 
nondas  ! 

When  Pompey,  after  finishing  the  war  against  Mithri- 
dates,  went  to  visit  the  celebrated  philosopher  Posidonias, 
he  prohibited  the  lictors  from  knocking  at  the  door  with 
their  sticks,  as  was  the  custom.  Thus,  says  PHny,  were 
the  fasces  of  the  man  who  had  seen  the  East  and  the 
West  prostrated  before  him,  lowered  before  the  humble 
dwelling  of  a  learned  man  ! 

Cffisar,  who  may  also  be  claimed  as  a  man  of  letters, 
allows  us  to  perceive,  in  at  least  twenty  places  in  his  im- 
mortal Commentaries,  what  rank  was  occupied  in  his  own 
esteem  by  the  various  faculties  with  which  nature  had  so 
liberally  endowed  him.  How  brief  he  is,  how  rapid  in 
relating  combats  and  battles  !  See,  on  the  contrary, 
whether  he  thinks  any  detail  superfluous  in  the  descrip- 
tion of  the  temporary  bridge  by  means  of  which  his  army 
crossed  the  Rhine.  It  is  because  success  depended  here 
on  the  conception,  and  the  conception  was  exclusively 
his  own. 

It  has  also  been  already  remarked,  that  the  part  which 


HEKOIC    ELOQUENCE.  457 

Ca2sar  by  preference  attributed  to  himself  in  tlie  events 
of  the  war,  that  of  which  he  seems  to  have  been  most 
proud,  was  a  moral  influence.  Ccesar  harangued  his  army, 
is  constantly  the  first  phrase  with  which  he  begins,  when 
describing  a  battle  gained.  And  Ccesar  did  not  arrive 
soon  enough  to  talk  to  his  soldiers,  to  exhort  them  to  con- 
duct themselves  tvell,  is  the  general  accompaniment  of  the 
recital  of  a  surprise  or  of  a  momentary  rei^ulse.  The 
general  frequently  undertakes  to  efface  himself  in  the 
presence  of  the  orator.  And  the  judicious  Montaigne 
remarks  :  "  His  language,  truly,  in  many  places,  does 
him  notable  service  !  " 

Meantime,  without  transition,  without  even  insisting- 
on  the  well-known  exclamation  of  Frederic  the  Great : 
'■'■Iwould  rather  have  written  the  Century  of  Louis  XIV. 
by  Voltaire,  than  have  gained  a  hundred  battles."  I 
come  to  Napoleon.  As  we  must  hasten  on,  I  will  not 
recall  the  celebrated  proclamations,  written  under  the 
shade  of  the  Egyptian  Pyramids  by  the  Member  of  the 
Institute,  Commander-in-Chief  of  the  army  of  the  East ; 
nor  the  treaties  of  peace,  in  which  monuments  of  art  or 
of  science  were  the  price  of  the  vanquished  people's  ran- 
som ;  nor  the  profound  esteem  which  the  general,  become 
emperor,  never  ceased  to  feel  for  the  Lagranges,  the  La- 
places,  the  Monges,  the  Berthollets,  nor  the  riches  nor 
the  honoui's  which  he  showered  down  upon  them.  An 
anecdote,  little  known,  will  lead  more  directly  to  my 
aim. 

Everybody  remembers  the  decennial  prizes.  The  four 
classes  of  the  Institute  had  sketched  out  rapid  analyses 
of  the  progress  made  in  the  sciences,  letters,, and  arts. 
The  presidents  and  the  ^secretaries  were  to  be  called  in 
succession  to  read  them  to  Napoleon,  in  the  presence  of 

SEC.  SER.  20 


458  JAMES    WATT. 

the  great  dignitaries  of  the  empii-e,  and  the  Council  of 
State. 

On  the  27th  of  February,  1808,  it  came  to  the  turn 
of  the  French  Academy.  As  may  be  easily  supposed, 
the  assembly  on  that  day  was  even  more  numerous  than 
usual :  who  does  not  think  himself  a  judge  in  matters  of 
taste  ?  Chenier  reads.  He  is  listened  to  with  attentive 
silence  :  but  all  at  once  he  is  interrupted  by  the  emperor, 
who,  putting  his  hand  on  his  heart,  his  body  leaning  for- 
ward, his  voice  affected  by  a  visible  emotion,  exclaimed  : 
"It  is  too  much,  too  much.  Gentlemen,  you  overpower 
me  ;  words  fail  me  in  which  to  express  my  gratitude'! " 

I  leave  you  to  imagine  the  deep  surprise  of  the  many 
courtiers  who  witnessed  this  scene  ;  those  men  who  from 
flattery  to  flattery  had  come  at  last  to  say  to  their  mastei-, 
and  without  his  appearing  astonished  at  it :  "  When 
God  had  created  Napoleon,  he  felt  the  want  of  re- 
pose ! " 

But  what  then  were  the  words  that  went  so  exactly,  so 
directly  to  the  heart  of  Napoleon  ?  These  words  were 
the  following  : — 

"  In  camps  where,  far  from  the  calamities  of  the  inte- 
rior, national  glory  was  unalterably  preserved,  another 
style  of  eloquence  arose,  unknown  until  then  to  modern 
nations.  We  must  even  acknowledge,  that  when  we  read 
in  ancient  authors  harangues  from  the  most  renowned 
leaders,  we  are  often  tempted  to  admire  only  the  talent 
of  the  historians  in  them.  But  here,  it  is  impossible  to 
doubt ;  the  monuments  exist :  history  has  only  to  collect 
them  together.  It  was  from  the  armies  of  Italy  that 
those  beautiful  proclamations  emanated,  in  which  the 
conqueror  of  Lodi  and  of  Arcoli,  created  at  the  same 
time  a  new  system  of  warfarp,  and  a  new  style  <if  mill- 


KSTI3IATI0N    OF    WATT's    MERITS.  459 

tary  eloquence,  of  which  he  will  for  ever  remain  the 
model." 

On  the  28th  of  February,  the  clay  after  the  celebrated 
sitting  that  I  have  just  described,  the  Moniteur,  with  its 
known  fidelity,  published  an  answer  from  the  emperor  to 
Chenier's  discourse.  It  was  cold,  laconic,  unmeaning  ; 
it  had,  in  short,  all  the  chai'acteristics  that  other  people 
would  say  are  those  of  an  official  document.  As  to  the 
incident  that  I  recorded,  there  was  no  allusion  to  it ;  a 
wretched  concession  to  predomuiant  opinions,  to  the  sus- 
ceptibilities of  a  military  etiquette  !  The  master  of  the 
world,  to  use  Pliny's  expression,  ceding  for  a  moment  to 
his  inward  feeling,  had  not  the  less  bowed  his  fasces  to 
the  literary  title  awarded  to  him  by  an  Academy. 

These  reflections  on  the  comparative  merits  of  the 
man  of  letters  and  the  man  of  arras,  although  not  chiefly 
suggested  by  what  is  said,  by  what  is  done  under  our 
ocular  experience,  would  not  be  inapplicable  to  the 
country  of  James  Watt.  I  travelled  not  long  since 
through  England  and  Scotland.  The  good  will  with 
which  I  was  received,  authorized  questions  on  my  part, 
as  dry,  as  pointed,  as  direct,  as  might,  under  other  cir- 
cumstances, have  come  only  from  the  president  of  a  com- 
mission of  inquiry.  Already  fully  preoccupied  with  the 
obligation  I  should  be  under,  at  my  return,  to  give  a 
judgment  on  the  illustrious  mechanic ;  already  feeling 
uneasy  at  the  solemn  character  of  the  meeting  before 
which  I  am  speaking,  I  had  prepared  the  following 
question:  "What  do  you  think  of  the  influence  that 
Watt  had  on  the  riches,  on  the  power,  and  on  the  pros- 
perity of  England?"  I  do  not  exaggerate  in  saying 
that  I  addressed  this  question  to  upwards  of  a  hundred 
])crson^   belonging  to  all  classes  of  society,  to  all  varie- 


460  JAMES    WATT. 

ties  of  political  opinions,  from  the  most  violent  radicals 
to  the  most  obstinate  conservatives.  The  answer  was 
always  the  same ;  every  one  placed  the  services  of  our 
academician  above  all  comparison ;  each  man  quoted, 
besides,  the  discourses  pronounced  at  the  meeting  in 
which  the  Westminster  statue  was  voted,  as  the  faithful 
and  unanimous  expression  of  the  sentiments  of  the  Eng- 
lish nation.     What  did  these  discourses  say  ? 

Lord  Liverpool,  Prime  Minister  of  the  Crown,  calls 
Watt,  "  one  of  the  most  extraordinary  men  that  England 
ever  produced,  one  of  the  greatest  benefactors  to  the 
human  race."  He  declared  that  "  his  inventions  have 
augmented  the  resources  of  his  country  and  of  the  whole 
world,  to  an  incalculable  degree."  Then,  considering 
the  question  in  a  political  point  of  view,  he  added, — "  I 
have  lived  at  a  time,  when  the  success  of  a  war  depended 
on  the  possibility  of  pushing  our  fleets  out  of  port  with- 
out loss  of  time ;  contrary  winds  prevailed  during  whole 
months,  and  would  have  entirely  upset  the  intentions  of 
government.  Thanks  to  the  steam-engine,  such  difficul- 
ties have  disappeared  for  ever."  * 

"  Direct  your  attention,"  Sir  Humphry  Davy  ex- 
claimed, "  to  the  metropolis  of  this  powerful  empire,  to 
our  townis,  to  our  villages,  to  our  arsenals,  to  our  manu- 
factories ;  examine  our  subterranean  cavities,  and  the 
works  accomplished  on  the  surface  of  the  globe ;  con- 
template our  rivers,  our  canals,  the  seas  which  bathe  our 
shores ;  you  will  everywhere  find  proofs  of  the  eternal 
benefits  conferred  by  that  great  man." 

The  illustrious  President  of  the   Royal  Society  also 

*  It  should  be  obseryed  that  during  the  wars  of  which  Lord  Liver- 
pool had  any  cognizance,  steam  had  not  been  applied  to  this  purpose. 
—  Translator. 


ESTIMATION    OF    WATT's    MERITS.  461 

said  :  "  The  genius  exerted  by  Watt  in  his  admirable 
inventions,  has  contributed  more  to  show  the  practical 
utility  of  science,  to  enlarge  the  power  of  man  over  the 
material  world,  to  multii)ly  and  to  spread  the  conven- 
iences of  life,  than  the  efforts  of  any  other  man  of  mod- 
ern times."  Finally,  Davy  does  not  hesitate  to  place 
Watt  above  Archimedes ! 

Then  Huskisson,  Minister  of  the  Board  of  Trade, 
divesting  himself  for  a  moment  of  the  character  (qualite) 
of  an  Englishman  (?),  proclaims,  that  compared  in  their 
bearings  on  the  happiness  of  the  whole  human  species, 
Watt's  inventions  would  still  appear  to  him  to  deserve 
the  highest  admiration.  He  explains  in  what  manner 
the  economy  of  labour,  the  indefinite  multiplication  and 
cheapness  of  industrial  products,  contribute  to  excite  and 
to  spread  knowledge.  He  said  :  "  The  steam-engine 
is  not  only,  in  the  hands  of  man,  the  most  powerful 
instrument  they  use  to  alter  the  face  of  the  physical 
world ;  it  acts  also  as  a  moral  and  irresistible  lever  for 
pushing  on  the  great  cause  of  civilization." 

From  this  point  of  view.  Watt  appeared  to  him  in  a 
distinguished  rank  among  the  benefactors  of  humanity. 
As  an  Englishman  he  does  not  hesitate  to  say  that  with- 
out Watt's  creations  the  British  nation  could  not  have 
stood  the  immense  expenses  of  its  recent  war  with 
France. 

The  same  idea  may  be  observed  in  the  discourse  of 
another  member  of  Parliament,  in  that  of  Sir  James 
Mackintosh :  see  whether  he  expresses  himself  in  less 
positive  terms.  "It  was  the  inventions  of  Watt  that 
enabled  England  to  sustain  the  severest,  the  most  dan- 
gerous conflicts  that  she  was  ever  engaged  in."  Every- 
thing considered,  Mackintosh  declares,  without  hesitation, 


462  JAMES    WATT. 

that  "  no  man  has  had  more  evident  claim  than  Watt  to 
the  homage  of  his  country,  to  the  respect  and  venei-ation 
of  future  ages." 

I  will  now  give  some  numerical  estimates,  some  num- 
bers, which  to  my  mind  are  more  eloquent  still  than  the 
several  passages  which  I  have  been  quoting. 

Mr.  Boulton,  junior,  announced  that  in  the  year  1819, 
the  manufactory  of  Soho  alone  had  already  made  Watt's 
engines  equal  to  the  labour  of  a  hundred  thousand 
horses  ;  that  the  saving  arising  from  the  substitution  of 
these  machines  for  animal  power  amounted  to  seventy- 
five  millions  of  francs  (three  millions  sterling)  per  an- 
num. In  England  and  Scotland  at  that  time,  there 
existed  upwards  of  ten  thousand  steam-engines.  They 
did  the  work  of  five  hundred  thousand  horses,  or  of 
between  three  and  four  millions  of  men  ;  with  an  annual 
saving  of  three  or  four  hundred  millions  of  francs  (twelve 
or  sixteen  miUions  sterling).  And  these  results  must  by 
this  time  be  more  than  doubled. 

I  have  thus  abridged  what  was  thought  of  Watt  by 
the  ministers,  the  statesmen,  the  learned  men,  and  the 
industrial  men — the  best  able  to  appreciate  him.  Gen- 
tlemen, the  creator  of  six  or  eight  millions  of  workmen, 
indefatigable  and  assiduous  workmen,  among  whom 
authority  will  never  have  to  repress  combination  or  riot, 
workmen  on  five  centimes  per  day  (one  half-penny)  ; 
this  man,  who,  by  brilliant  inventions,  gave  England  the 
means  of  maintaining  a  desperate  struggle,  during  which 
its  very  nationahty  was  at  stake,  this  new  Archimides, 
this  benefactor  of  the  whole  human  race,  whose  memory 
will  be  blessed  by  future  generations — what  was  done  to 
honour  him  during  his  life  ? 

The  peerage  is  in  England  the  first  of  its  dignities,  its 


CLAIMS    FOR    A    PEERAGE.  463 

highest  reward.  You  will  naturally  suppose  that  Watt 
was  made  a  peer. 

Such  a  thing  was  not  even  thought  of ! 

To  speak  honestly,  so  much  the  worse  for  the  peer- 
age, which  would  have  been  honoured  by  the  name  of 
Watt ! 

Such  a  neglect,  however,  in  a  nation  so  justly  proud 
of  its  great  men,  might  well  astonish  me.  And  when  I 
inquired  the  cause,  what  do  you  think  they  answered  ? 
"  The  dignities  of  which  you  speak  are  reserved  for 
officers  of  the  army  and  navy,  for  influential  orators  in 
the  House  of  Commons,  for  members  of  the  nobility. 
It  is  not  the  fashion  (I  do  not  invent,  I  quote  precisely,) 
it  is  not  the  custom,  to  grant  them  to  learned  men,  to 
literary  men,  to  artists,  to  engineers ! "  I  know  well 
that  it  was  not  the  fashion  under  Qyeen  Anne,  since 
Newton  was  not  made  a  peer  of  England.*  But  after 
a  century  and  a  half  of  progress  in  science  and  in  phi- 
losophy, when  each  of  us  during  the  short  course  of  his 
life  has  seen  so  many  wandering  kings  cast  off,  proscribed, 
succeeded  on  their  thrones  by  soldiers  without  genealogy, 
sons  of  their  sword,  was  it  not  allowable  to  think  that  it 
had  become  obsolete  to  divide  men  into  folds  ;  that  none 
would  any  longer  say  to  their  faces,  as  in  the  inflexible 
code  of  the   Pharaohs — "Wliatever   be  your    services, 

*  The  whole  truth  should  have  been  told.  Newton,  though  unfor- 
tunatel}'  not  made  a  peer,  was  never  hidden  under  a  bushel.  He  was 
knighted  by  Queen  Anne,  and  courted  by  King  George  I.  and  by  the 
Princess  of  Wales,  afterwards  Queen  Caroline.  He  was  President  of 
the  Royal  Society,  a  Member  of  Parliament,  a  Master  of  the  Mint; 
and  at  his  interment  the  pall  was  supported  by  the  Lord  High  Chan- 
cellor, the  Dukes  of  Montrose  and  Roxburgh,  and  the  Earls  of  Pem- 
broke, Sussex,  and  Macclesfield.  Moreover,  our  author  seems  to 
have  excluded  the  host  of  lawyer-peers  from  the  class  "  learned 
men." — Translator. 


464  JAMES    WATT. 

your  virtues,  your  knowledge,  not  one  of  you  shall  over- 
step the  boundary  of  your  caste ; "  that  a  foolish  custom, 
in  short,  since  such  a  custom  exists,  should  no  longer 
blot  the  institutions  of  a  great  nation  ! 

Let  us  trust  to  the  future.  A  time  will  come  when  the 
science  of  destruction  will  bow  before  the  arts  of  peace  ; 
when  the  genius  which  multiplies  our  powers,  which 
creates  new  products,  which  spreads  comfort  among 
masses  of  people,  will  occupy  that  place  in  the  general 
esteem  of  mankind,  that  reason  and  good  sense  assign  to 
it  already. 

"Watt  will  then  appear  before  the  grand  jury  of  the 
two  worlds.  Every  one  will  see  him,  aided  by  his  steam- 
engine,  penetrate  in  a  few  weeks  into  the  bowels  of  the 
earth  to  depths  where,  before  him,  we  could  not  have 
arrived  without  a  century's  most  painful  efforts  ;  he  w'll 
dig  spacious  galleries  there,  and  will  clear  them  in  a 
few  minutes  of  the  immense  volumes  of  w^ater  that  used 
to  inundate  them  daily ;  he  will  drag  from  a  virgin  soil 
the  inexhaustible  riches  that  nature  deposited  there. 

Uniting  delicacy  with  power,  Watt  will  twist  with 
equal  success  the  enormous  strands  of  the  colossal  cable 
by  which  the  man-of-war  moors  itself  in  the  midst  of  the 
chafed  ocean — and  the  microscopic  filaments  of  that  lace, 
of  that  aerial  web,  which  forms  so  favourite  a  portion  of 
the  various  dresses  introduced  by  fashion. 

A  few  oscillations  of  this  same  machine  will  restore  to 
agriculture  vast  swamps  ;  thus  fertile  countries  will  be 
rescued  from  the  pei-iodical  and  fatal  miasma  that  used 
to  be  fostered  there  by  the  burning  summer-suns. 

The  great  mechanical  powers  that  we  used  to  have  to 
seek  in  mountainous  regions,  at  the  foot  of  large  water- 
falls, now,  thanks  to  Watt's  discovery,  will  arise  at  will, 


RESULTS    OF    STEAM.  465 

in  a  compact  form,  and  without  annoyance  in  the  midst 
of  towns,  in  every  floor  of  a  house. 

The  intensity  of  this  power  will  vaiy  according  to  the 
will  of  the  mechanic  ;  it  will  not  depend  as  formerly  on 
the  most  inconstant  of  natural  causes :  on  atmospheric 
meteorology. 

The  various  branches  of  a  manufactory  can  be  united 
in  one  common  area,  and  under  one  roof. 

The  industrial  products,  whilst  undergoing  improve- 
ment, will  also  be  reduced  in  price. 

The  population  well-fed,  well-dressed,  well-warmed, 
will  increase  rapidly ;  it  will  cover  every  part  of  the 
territory  with  elegant  habitations  ;  even  those  parts  that 
might  justly  be  called  the  steppes  of  Europe,  and  which 
from  the  aridity  of  ages  seemed  to  be  condemned  to  re- 
main the  exclusive  domain  of  wild  beasts. 

In  a  few  years  hamlets  will  become  important  cities  : 
in  a  few  years  boroughs,  such  as  Birmingham,  where 
there  used  to  be  scarcely  thirty  streets,  will  rise  to  be 
ranked  among  the  largest  cities,  the  handsomest  and  the 
richest  of  a  powerful  kingdom. 

Installed  on  board  ship,  the  steam-engine  will  replace 
a  hundi-edfold  the  efforts  of  the  triple,  of  the  quadruple 
banks  of  rowers,  from  whom  our  ancestors  required  a 
degree  of  labour  classed  among  the  punishments  of  the 
worst  criminals. 

By  the  aid  of  a  few  tons  of  coals,  man  will  conquer 
the  elements  ;  he  will  laugh  at  calms,  at  contrary  winds, 
at  storms. 

Passages  from  one  country  to  another  will  become 
more  rapid  ;  the  time  of  the  steamboat's  arrival  can  be 
foretold  as  correctly  as  that  of  a  public  land  conveyance ; 
you  will  no  more  go  to  the  sea-shore  for  weeks,  or  even 

20  * 


466  JAMES    WATT. 

whole  months,  your  heart  a  prey  to  cruel  anguish,  seeking 
with  an  anxious  eye  along  the  horizon,  for  the  uncertain 
glimpse  of  the  ship  that  is  to  restore  to  you  a  father,  a 
mother,  a  brother,  or  a  friend. 

To  conclude,  the  steam-engine,  dragging  in  its  train 
some  thousands  of  travellers,  will  run  along  the  railways 
much  faster  than  the  best  blood  horse  bearing  only  his 
light  jockey  along  the  race-course. 

There,  Gentlemen,  is  a  very  brief  sketch  of  the  bene- 
fits bequeathed  to  the  world  by  the  machine,  the  germs 
of  which  Papin  had  deposited  in  his  works,  and  which, 
after  so  many  ingenious  efforts,  Watt  has  brought  to  an 
admirable  perfection.*    Posterity  certainly  will  not  weigh 

*  A  trnnslator  sliould  not,  perhaps,  enter  the  lists,  but  he  may  in- 
trude a  remark.  It  is  difficult  to  opine  why  our  author  should  bestir 
himself  so  eagerly  to  give  Watt  the  composition  of  water,  and  yet  im- 
pair his  grand  claim  to  universal  homage  by  foisting  in  the  names  of 
Eivanlt,  De  Caus,  and  others  as  inventors:  the  early  engines  were 
mere  toys  and  pumps,  and  therefore  foreign  to  tlie  marvellous  and 
almost  animated  machine  which  is  now  in  use.  Some  of  Watt's  ex- 
cogitations and  contrivances,  the  product  of  lengthy  intellectual 
struggles,  are  slurred  over,  while  others  are  not  even  alluded  to;  and 
the  difficulties  he  had  to  combat  with  in  metallurgy  are  altogether 
omitted. 

We  ought  to  be  cautious  in  attaching  an  undue  value  to  mere  saga- 
cious surmises,  unsupported  by  legitimate  proof;  for  notions  may  arise 
without  being  brought  to  bear;  and  simultaneous  ideas  may  be  formed 
without  the  parties  being  indebted  to  each  other.  M.  Arago  cannot 
tell  whether  De  Caus  actually  made  an  engine ;  but  surely  he  ought, 
as  a  self- constituted  historical  umpire,  to  have  consulted  the  published 
Travels  of  Cos7no  III.  ( Grand  Duke  of  Tuscany)  in  England,  in  the  reign 
of  Charles  II.,  and  he  would  there  have  found  that  the  Marquis  of 
Worcester  actually  did  make  one  (see  note  to  page  378).  Now  for  all 
that  is  admirable  in  the  structure  of  the  mighty  piece  of  mechanism, 
and  really  marvellous  in  its  application,  Watt  was  not  a  mere  im- 
prover, but  a  highly-gifted  inventor.  We  therefore  insist  that,  to  all 
its  useful  intents  and  purposes,  the  present  Steam-engine  is  a  British 
production.     Thus  in  transcendental  science,  although  preceding  and 


ACADEMICAL    HONODUS.  467 

them  with  other  labours  that  have  been  too  much  vaunted  ; 
and  whose  real  influence  at  the  tribunal  of  I'eason,  will 
always  remain  circumscribed  to  a  circle  of  a  few  individ- 
uals, and  a  short  compass  of  years. 

They  used  formerly  to  appeal  to  the  age  of  Augustus, 
then  to  the  age  of  Louis  XIV.  Some  eminent  minds 
have  already  maintained  that  it  would  be  justice  to  speak 
of  the  age  of  Voltaire,  of  Rousseau,  of  Montesquieu. 
As  to  myself,  I  do  not  hesitate  to  announce,  that  when  to 
the  immense  services  already  rendered  by  the  steam- 
engine,  all  the  wonders  are  added  that  it  still  promises, 
grateful  nations  will  also  speak  of  the  ages  of  Papin  and 
of  Watt ! 


ACADEMICAL    TITLES    WITH    WHICH    WATT    WAS    IN- 
VESTED. 

A  biography  of  Watt,  intended  to  make  part  of  our 
collection  of  memoirs,  would  certainly  be  incomplete  if 
it  did  not  contain  a  list  of  the  academical  titles  with  which 
the  illustrious  engineer  was  invested.  This  list,  more- 
over, will  occupy  only  a  few  lines : — 

contemporary  philosophers  had  made  conjectures  on  the  subject  that 
did  not  difter  widely  from  truth,  Newton,  by  an  inductive  ascent 
through  a  train  of  abstruse  investigations  to  its  principle,  and  thereby 
detecting  and  expounding  its  laws,  is  justly  recognized  as  the  author 
of  the  sublime  hypothesis  of  Gravitation.  Who  will  deny  to 
Herschel  the  merit  of  discovering  the  planet  Uranus,  since  Flamsteed 
had  previously  observed  it  as  a  star  ?  Or  still  later,  because  some 
philosophers  thought  that  there  might  exist  a  planet  exterior  to 
Uranus,  who  would  deny  the  palm  to  those  whose  energies  were 
awakened  by  the  orbital  tremblings  of  that  outer  body  to  the  splendid 
discovery  of  Neptune  V  In  reality,  De  Caus,  Worcester,  and  Fapin 
may  be  placed  with  respect  to  Watt,  as  Gilbert,  Kepler,  and  Hooke 
are  to  Newton;  or  as  Lambert,  De  Zach,  and  Bode  will  be  to  Le 
Vcrrier  and  Atiams. —  Translalor. 


468  JAMES    WATT. 

Watt  became : 

Fellow  of  the  Royal  Society  of 

Edinburgh in  1784  ; 

Fellow  of  the  Royal  Society  of 

London in  1785  ; 

Fellow  of  the  Society  of  Batavia      .  in  1787  ; 
By  a  spontaneous  and  unanimous 

vote,  the  Senate  of  the  Uni- 
versity of  Glasgow  awarded  to 

Watt  the  honorary  degree  of 

Doctor  of  Laws  .  .  .  .  in  1806  ; 
Correspondent  of  the  Institute  .  .  in  1808  ; 
The  Academy  of  Sciences  of  the 

Listitute  paid  Watt  the  highest 

honour  there  is  in  its  awaixls, 

by   naming    him   one   of    its 

eight  Foreign  Associates       .         .  in  1814. 


APPENDIX. 


RETRANSLATION  OF  AN  HISTOEICAL  NOTE  BY  LORD 
BROUGHAM,  ON  THE  DISCOVERY  OF  THE  COMPOSITION 
OF   WATER. 

There  is  no  doubt  that  in  England,  at  least,  tke  researches 
respecting  the  composition  of  water  originated  in  Warltire's 
experiments  related  in  the  fifth  volume  of  Priestley.*  Caven- 
dish cites  them  expressly  as  having  given  him  the  idea  of  his 
work  {Phil.  Trans.  1784,  p.  126).  Warltire's  experiments  con- 
sisted in  the  combustion  of  a  mixture  of  oxygen  and  hydrogen, 
by  means  of  the  electric  spark,  and  in  closed  vessels.  Two  re- 
sults wei'e  reported  therefrom:  1.  a  perceptible  loss  of  weight; 
2.  the  precipitation  of  some  humidity  on  the  sides  of  the  vessels. 

Watt  inadvertently  said  in  the  note  to  page  332,  of  his 
Memoir  (Phil.  Trans.  1784),  that  the  aqueous  precipitation 
was  observed  for  the  first  time  by  Cavendish ;  but  Cavendish 
himself  declares,  p.  127,  that  Warltire  had  perceived  the  slight 
aqueous  deposit,  and  quotes  on  this  subject  Priestley's  fifth 
volume.  Cavendish  could  not  ascertain  any  loss  of  weight. 
He  remarks  that  Priestley's  essays  had  led  him  to  the  same 
result,-\  and  adds  that  the  humidity  which  was  deposited  con- 

*  Warltire's  letter,  dated  Birmingham,  18th  AprU,  1781,  was  pub- 
lished by  Dr.  Priestley  in  the  second  volume  of  his  Experiments  and 
Observations  relating  to  various  l^ranches  of  Natural  Philosophy^  loiih  a 
continuation  of  the  Observations  on  Air,  forming,  in  short,  tlie  fifth 
volume  of  the  Experiments  and  Observations  on  different  Kinds  oj"  Air, 
published  at  Birmingham  in  1781. — {Note  by  Mr.  \Valt,jun.) 

t  The  note  by  Mr.  Cavendish  to  p.  127,  seems  to  imply  that  Priest- 


470  JAMES    WATT. 

tained  no  impurity  (literally  no  particle  of  soot  or  of  sooty 
matter).  After  a  great  number  of  trials,  Cavendish  perceived 
that  if  a  mixture  of  common  and  of  inflammable  air  is  ignited, 
a  mixture  formed  of  1000  measures  of  the  former  and  423  of 
the  latter,  "  about  one  fifth  of  the  common   and  nearly  the 

ley  had  not  perceived  any  loss  of  weight;  but  I  do  not  find  this  asser- 
tion anywhere  in  the  Memoirs  of  the  Birmingham  chemist. 

Warltire's  earliest  experiments  on  the  combustion  of  gas  were  made 
in  a  copper  globe  which  weighed  398  grammes,  and  the  volume  was 
170  centilitres.  The  author  wished  "  to  decide  whether  heat  is,  or  is 
not  heavy." 

Warltire  first  describes  the  method  of  mixing  the  gases,  and  of  ad- 
justing the  scales;  he  then  says,  "I  always  carefully  weighed  the 
vessel  filled  with  common  air,  so  that  the  difference  of  weight  after 
the  addition  of  the  inflammable  air  enabled  me  to  judge  whether  the 
mixture  had  been  efiected  in  the  desired  proportions.  The  passage  of 
the  electric  spark  rendered  the  globe  hot.  After  it  had  cooled  by  ex- 
posure to  the  air  of  the  room,  I  suspended  it  again  on  the  scales.  I 
alwaj-s  found  a  loss  of  weight,  but  there  were  differences  between  oae 
experiment  and  another.     The  mean  loss  was  129  milligrammes." 

Warltire  continues  as  follows:  "I  have  exploded  my  airs  in  glass 
vessels  since  I  saw  you  recently  do  so  yourself  (Priestley),  and  I  have 
observed,  as  you  did,  that  however  dry  and  clean  the  vessel  might 
be  before  the  explosion,  it  was  afterwards  covered  with  dew  and  a 
black  sooty  substance.'" 

la  comparing  all  these  claims,  does  not  the  merit  of  having  first 
perceived  tlie  dew  belong  to  Priestley  ? 

In  the  few  remarks  that  Priestley  has  added  to  his  correspondent's 
letter,  he  confirms  the  loss  of  weight,  and  adds,  "  Still,  I  do  not  think 
that  the  bold  opinion  of  the  latent  heat  of  bodies  entering  as  a  sensible 
part  of  their  weight,  can  be  admitted  without  making  experiments  on  a 
larger  scale.  If  that  is  confirmed  it  will  be  a  very  remarkable  fact, 
and  one  that  will  do  infinite  credit  to  Warltire's  sagacity." 

And  Priestley  continues,  "  We  must  say  also,  that  at  the  moment 
when  he  (Warltire)  saw  the  dew  on  the  interior  surface  of  the  closed 
glass  vessel,  he  said  that  it  confirmed  an  opinion  which  he  had  long 
entertained,  the  opinion  that  common  air  parts  with  its  humidity  when 
it  is  phlogisticated." 

It  is  evident  then  that  Warltire  explained  the  dew  by  the  simple 
mechanical  precipitation  of  the  hygrometric  water  contained  in  cam- 
mon  air. — (Note  by  Mr.  \Vatt,jun.) 


LORD    UROUGHAM's    APPENDIX.  471 

whole  of  the  inflammable  air  lose  their  elasticity,  and  form  by 

their  condensation  the  dew  that  covers  the  glass On 

examining  the  dew,  Cavendish  found  that  it  consisted  of  pure 
■water He  thence  concluded  that  nearly  all  the  in- 
flammable air  and  about  one  sixth  of  the  common  air  are 
turned  into  pure  water." 

In  a  similar  way,  Cavendish  burned  a  mixture  of  inflam- 
mable air,  and  dephlogisticated  air  (or  hydrogen  and  oxygen)  ; 
the  fluid  that  was  jirecipitated  was  always  more  or  less  acid, 
according  as  the  gas  burned  with  the  inflammable  air  contained 
more  or  less  phlogiston.  The  acid  thus  engendered  was  nitric 
acid. 

Mr.  Cavendish  ascertained  that  nearly  the  whole  of  the  in- 
flammable air  and  the  dephlogisticated  air  are  converted  into 
pure  water ;  also,  that  if  those  airs  could  be  obtained  in  a  per- 
fectly pure  state,  the  whole  would  be  condensed.  If  common 
air  and  inflammable  air  do  not  yield  any  acid  when  they  are 
burnt,  it  is,  according  to  our  author,  because  the  heat  is  not 
then  intense. 

Cavendish  declares  that  his  experiments,  except  in  as  far  as 
they  relate  to  the  acid,  were  made  in  the  summer  of  1781, 
and  that  Priestley  was  aware  of  them.  He  adds,  "  One  of  my 
friends  gave  some  account  of  them  to  Lavoisier,  in  the  course 
of  last  spring  (the  spring  of  1783),  and  also  of  the  result  that 
I  had  inferred  from  them,  that  is  to  say,  that  dephlogisticated 
air  is  water  deprived  of  its  phlogiston.  But  at  that  time,  La- 
voisier was  so  far  from  thinking  that  such  a  opinion  was  legiti- 
mate, that  until  the  moment  when  he  determined  to  repeat 
the  experiments  himself,  he  felt  some  difficulty  in  believing 
that  nearly  the  whole  of  the  two  airs  could  be  converted  into 
water." 

The  friend  alluded  to  in  the  preceding  passage  was  Dr., 
since  become  Sir  Charles  Blagden.  It  is  a  remarkable  cir- 
cumstance, that  this  passage  in  the  work  of  Mr.  Cavendish 
should  not  have  formed  part  of  the  original  Memoir  that  was 
presented  to  the  Royal  Society.  The  Memoir  seems  to  be 
written  in  the  author's  own  handwriting ;  but  the  paragraphs 


472  JAMES    WATT. 

134  and  135  were  not  there  at  first ;  they  are  added,  and  an 
indication  is  given  as  to  where  they  belong ;  the  writing  is  no 
longer  that  of  Cavendish  ;  these  additions  are  in  the  hand- 
writing of  Blagden.  And  it  must  have  been  he  who  gave  all 
the  relative  details  to  Lavoisier,  for  it  is  not  said  that  Caven- 
dish held  any  direct  correspondence  with  him. 

The  date  of  the  reading  of  Cavendish's  Memoir  was  the  15th 
of  January,  1 784.  The  volume  of  the  Philosophical  Trans- 
actions, of  which  this  Memoir  forms  a  part,  did  not  appear  till 
about  six  months  after. 

Lavoisier's  Memoir  (volume  of  the  Academy  of  Sciences  for 
1781)*  had  been  read  in  November  and  December,  1783. 
Various  additions  were  made  to  it  afterwards.  The  publica- 
tion took  place  in  1 784. 

This  Memoir  contained  a  description  of  the  experiments  of 
June,  1783,  at  which  Lavoisier  announces  that  Blagden  was 
present.  Lavoisier  adds,  that  this  English  physicist  informed 
him  "  that  Cavendish  having  already  burnt  inflammable  air  in 
closed  vessels,  had  obtained  a  very  sensible  quantity  of  water  ;" 
but  he  nowhere  says  that  Blagden  informed  him  of  the  con- 
clusions that  Cavendish  had  inferred  from  those  same  experi- 
ments. 

Lavoisier  declares,  in  the  most  express  manner,  that  the 
weight  of  the  water  is  equal  to  that  of  the  two  gases  that  were 
ignited,  unless,  contrary  to  his  own  opinion,  a  sensible  weight 
be  assigned  to  the  heat  and  to  the  light  that  were  disengaged 
during  the  experiment. 

This  account  does  not  agree  with  that  of  Blagden,  which, 
according  to  all  probability,  was  written  as  a  refutation  to 
Lavoisier's  relation,  after  the  reading  of  Cavendish's  Memoir, 
and  before  the  volume  of  the  Academy  of  Sciences  had  reached 
England.  This  volume  appeared  in  1784,  and  assuredly  it 
could  not  have  reached  London,  either  when  Cavendish  read 
his  paper  to  the  Royal  Society,  or  still  less  when  he  wrote  it. 
We  must  remark,  besides,  that  in  the  passage  of  Cavendish's 

*  The  date  1781  appears  to  be  a  clericiil  error  for  11  Si.— Translate . 


LORD    brougham's    APPENDIX.  473 

manuscript  Memoir,  in  the  handwriting  of  Blagden,  there  is 
only  one  communication  of  experiments  alluded  to :  one  com- 
munication to  Priestley.  The  experiments  are  there  said  to 
have  been  made  in  1781 ;  but  there  is  no  mention  of  the  date 
of  the  conununication.  Nor  are  we  informed  whether  the  con- 
clusions inferred  from  those  experiments,  and  which,  accord- 
ing to  Blagden,  were  communicated  by  him  to  Lavoisier  in  the 
summer  of  1783,  were  equally  included  in  the  communication 
made  to  Priestley.  This  chemist,  in  his  Memoir  written  before 
the  month  of  April,  1783,  read  in  June  of  the  same  year,  and 
quoted  by  Cavendish,  says  nothing  of  the  theory  of  the  latter, 
although  he  quotes  experiments. 

Several  propositions  flow  from  the  preceding  facts  : — 

1.  Cavendish,  in  the  Memoir  that  was  read  to  the  Royal 
Society  the  15th  of  January,  1784,  describes  the  capital  ex- 
periment of  the  combustion  of  the  oxygen  and  hydrogen  in 
closed  vessels,  and  cites  water  as  the  product  of  this  combus- 
tion ; 

2.  In  the  same  Memoir  Cavendish  deduces  from  these  same 
experiments  that  the  two  forementioned  gases  are  transformed 
into  water ; 

3.  In  an  addition  by  Blagden,  made  with  the  consent  of 
Cavendish,  the  date  of  the  summer  of  1781  is  assigned  to  the 
experiments  of  the  latter  ;  a  communication  to  Priestley  is 
quoted,  without  specifying  the  epoch,  without  mentioning  con- 
clusions, without  statinnj  even  when  those  conclusions  occurred 
to  the  miiid  of  Cavendish.  This  must  be  regarded  as  a  most 
material  omission  ; 

4.  In  one  of  the  additions  made  to  the  Memoir  by  Blag- 
den, Cavendish's  conclusion  is  related  in  the  following  words : 
Oxygen  gas  is  water  deprived  of  its  phlogiston.  This  addi- 
tion is  posterior  to  the  arrival  of  Lavoisier's  Memoir  in  Eng- 
land. 

It  may  moreover  be  remarked,  that  in  another  edition  to 
Cavendish's  Memoir,  written  by  the  hand  of  that  chemist,  and 
which  is  certainly  posterior  to  the  arrival  of  Lavoisier's  Me- 
moir in   England,   Cavendish  distinctly  asserts  for  the  first 


474  JAMES    WATT. 

time,  as  in  Lavoisier's  hypotliesis,  that  water  is  a  compound  of 
oxygen  and  hydrogen.  Perhaps  no  essential  difference  will 
be  found  between  this  conclusion  and  the  one  which  Caven- 
dish had  asserted  before,  that  oxygen  gas  is  water  deprived  of 
its  phlogiston,  for  to  render  them  identical  it  will  suffice  to 
look  upon  phlogiston  as  hydrogen  ;  but  to  say  of  water  that  it 
consists  of  oxygen  and  hydrogen,  is,  certainly  embracing  a 
neater  and  less  equivocal  conclusion.  I  add,  that  in  the  orig- 
inal part  of  his  Memoir,  in  that  which  was  read  to  the  Royal 
Society  before  the  arrival  of  Lavoisier's  Memoir  in  England, 
Cavendish  thinks  it  more  correct  to  consider  inflammable  air 
as  phlogisticated  water  than  as  pure  phlogiston." — (P.  140, 
Phil.  Trans,  for  1784.) 

Now  let  us  see  what  part  Watt  acted.  The  dates  will  here 
be  of  importance. 

It  appears  that  Watt  wrote  a  letter  to  Dr.  Priestley,  on  the 
2Gth  of  April,  1783,  in  which  he  discusses  the  experiment  of 
igniting  the  two  gases  in  closed  vessels,  and  that  by  it  he  came 
to  the  conclusion  that  water  is  composed  of  dephlogisticated 
air  and  phlogiston,  both  of  them  deprived  of  a  part  of  their 
latent  heat.* 

Priestley  deposited  the  letter  in  the  hands  of  Sir  Joseph 
Banks,  with  a  request  that  it  should  be  read  at  one  of  the  ear- 
liest meetings  of  the  Royal  Society.  But  Watt  afterwards 
wished  the  reading  to  be  deferred,  in  order  to  have  time  to 
see  how  his  theory  agreed  with  some  of  Priestley's  recent  ex- 


*  We  may  feel  quite  safe  in  deducing  from  the  inedited  correspond- 
ence of  Watt,  that  he  had  already  formed  his  theory  on  the  composi- 
tion of  water  in  December,  1782,  and  probably  earlier.  At  all  events, 
in  his  Memoir  of  the  21st  of  April,  1783,  Priestley  declares  that,  before 
his  own  experiments,  Watt  had  entertained  the  idea  that  steam  might 
be  transformed  into  permanent  gases. — (P.  416,  Phil.  Trans.  1783.) 

Watt  himself,  in  his  Memoir  (p.  335,  PJiil.  Trans.  1784),  declares 
that,  during  several  years,  he  had  entertained  an  opinion  that  air  is  a 
modification  of  water,  and  he  makes  known  in  detail  the  experiments 
and  the  reasonings  on  which  this  opinion  rested. — {Note  by  Mr.  Watt, 
jzmior.) 


LORD    brougham's    APPENDIX.  475 

periments.  In  short,  the  letter  was  not  read  till  April,  1784.* 
This  letter  was  incorporated  by  Watt  in  a  Memoir  addressed 
to  Deluc,  dated  26th  Nov.  ITSS.f  Many  new  observations, 
and  new  reasonings,  were  introduced  into  this  Memoir,  although 
nearly  the  whole  of  the  original  letter  was  preserved  in  it,  and 
in  the  printing  it  was  distinguished  from  the  additions  by  in- 
verted commas.  The  important  deduction,  previously  quoted, 
will  be  found  in  the  part  thus  marked.  We  read  also  that  the 
letter  was  communicated  to  several  Fellows  of  the  Royal  Soci- 
ety when  it  reached  Priestley  in  April,  1783. 

In  Cavendish's  Memoir,  such  as  it  was  when  read,  therd  was 
no  allusion  to  Watt's  theory ;  but  it  is  mentioned  in  an  addi- 
tion, entirely  in  the  handwriting  of  Cavendish,  posterior  to  the 
reading  of  Watt's  letters,  {Phil.  Trans.  1784,  p.  140.)  In  this 
addition  Cavendish  gives  his  reasons  for  not  liking  to  render 
his  conclusions  complicated  as  Watt  did,  with  considerations 
relative  to  the  disengagement  of  latent  heat ;  but  it  leaves  us 
in  doubt  on  the  question  as  to  whether  the  author  was  ever 
aware  of  the  letter  to  Priestley  of  April,  1783,  or  whether  he 
only  saw  the  letter  dated  26th  of  November,  1783,  and  read 
the  29th  of  April,  1784;  on  which  it  is  requisite  to  remark 
that  the  two  letters  appeared  in  the  Philosophical  Transactions 
united  in  one.  The  letter  to  Priestley  of  the  26th  April, 
1 783,  remained  some  time  (two  months  according  to  Watt's 
Memoir,)  in  the  hands  of  Sir  Joseph  Banks  and  other  Fellows 
of  the  Royal  Society,  during  the  spring  of  1783.  This  is  what 
we  learn  from  the  circumstances  related  in  the  note  at  p.  330. 
It  seemed  difficult  to  suppose  that  Blagden,  Secretary  of  the 

*  The  letter  to  Priestley  was  read  the  22d  of  April,  1784. 

t  Undoubtedly  tlie  Genevese  physicist,  then  in  Loudon,  received  it 
at  the  time.  It  remained  in  his  hands  until  Watt  heard  of  the  reading 
of  Cavendish's  Memoir  at  the  Royal  Society.  From  that  moment  mj' 
father  made  all  possible  arrangements  for  the  Memoir  addressed  to 
Deluc  and  the  letter  of  the  26th  of  April,  1783,  addressed  to  Dr.  Priest- 
ley, being  read  immediately  at  the  Royal  Society.  This  reading, 
claimed  by  Watt  for  the  Memoir  addressed  to  Deluc,  was  dated  29th 
of  A\n-\\,  n8i.—{Nole  by  Mr.  Watt,  jun.) 


476  JAMES    WATT. 

Society,  did  not  see  the  Memoir.  Sir  Joseph  Banks  must  have 
given  it  to  him,  since  he  intended  it  to  be  read  at  the  meeting, 
{Phil.  Trans.  1 784,  p.  330,  note.)  Let  us  add  that  as  the  letter 
•was  preserved  in  the  archives  of  the  Society,  it  was  in  charge 
of  JJlagden,  the  Secretary.  Would  it  be  possible  to  sup- 
pose that  the  person  whose  hand  wrote  the  remarkable  passage 
already  quoted,  relative  to  a  communication  made  to  Lavoisier, 
in  June,  1783,  of  the  conclusions  that  Cavendish  had  come  to, 
would  not  have  told  Cavendish  that  Watt  had  come  to  those 
conclusions  at  the  latest  in  April,  1783  ?  The  conclusions  are 
identical,  with  the  mere  difference  that  Cavendish  calls  de- 
phlogisticated  air  water  deprived  of  its  phlogiston,  and  tliat 
Watt  affirms  water  to  be  a  union  of  dephlogisticated  air  and 
phlogiston. 

We  must  remark  that  in  Watt's  theory  there  is  the  same 
uncertainty,  the  same  vagueness,  which  we  have  already  ob- 
served in  that  of  Cavendish,  and  that  it  also  proceeds  from  the 
use  of  the  term  phlogiston,  which  was  not  well  defined.*  In 
Cavendish  we  cannot  decide  whether  phlogiston  is  merely  in- 
flammable air,  or  whether  this  chemist  is  not  rather  inclined 
to  consider  a  combination  of  water  and  phlogiston  as  inflam- 
mable air.  Watt  says  expressly,  even  in  his  Memoir  of  the 
26th  November,  1783,  and  in  a  passage  that  does  not  form 
part  of  the  April  letter  in  1783,  that  inflammable  aii',  accord- 
ing to  his  ideas,  contains  a  small  quantity  of  water  and  a  great 
deal  of  elementary  heat. 

These  expressions  from  two  such  eminent  men,  should  be 
regarded  as  indicating  a  certain  degree  of  hesitation,  relative 
to  the  composition  of  water.  If  Watt  and  Cavendish  had  had 
a  precise  idea  that  water  results  from  the  union  of  two  gases 

*  In  a  note  to  his  Memoir  of  the  26th  of  November,  1783  (p.  331), 
we  read  the  following  remark  by  Watt:  "Anterior  to  Dr.  Priestlej'-'s 
experiments,  Kirwan  had  proved,  by  some  ingenious  deductions  bor- 
rowed from  other  facts,  that  inflammable  air  is  in  all  probability  the 
true  phlogiston  in  an  aerial  form.  Kirwan's  arguments  appear  to  me 
perfectly  convincing;  but  it  seems  more  suitable  to  establish  this  point 
of  the  question  by  direct  experiments." 


LORD    brougham's    APPENDIX.  477 

deprived  of  their  latent  beat,  from  the  union  of  the  bases 
of  inflammable  air  and  of  dephlogisticated  air ;  if  this  idea 
had  been  accompanied  in  their  minds  by  as  much  clearness 
as  in  that  of  Lavoisier,  they  would  certainly  have  avoided  the 
uncertainty  and  obscurity  which  I  have  pointed  out.* 

As  far  as  relates  to  Watt,  the  following  are  the  new  facts 
that  we  have  succeeded  In  establishing. 

1.  There  is  no  proof  that  anybody  had  given,  in  a  written 
document,  anterior  to  Watt,  the  present  theory  of  the  compo- 
sition of  water. 

2.  Watt  established  this  theory  during  the  year   1783,  in 

*  At  the  foot  of  p.  333,  of  the  Transactions  (for  1784),  in  a  part  of 
his  April  letter,  17S3,  printed  in  italics.  Watt  said:  "Are  we  not 
then  authorized  to  conclude  that  water  is  composed  of  dephlogisti- 
cated air  and  phlogiston  deprived  of  part  of  their  latent  or  elemen- 
tary heat;  that  dephlogisticated  air,  or  pure  air,  is  composed  of  water 
deprived  of  its  phlogiston  and  united  to  elementary  heat  and  light ; 
that  heat  and  light  are  contained  in  it  in  a  latent  state,  since  they  do 
not  affect  either  the  thermometer  or  the  eye  V  If  light  is  only  a  modi- 
fication of  heat,  or  a  peculiarity  in  its  existence,  or  a  constituent  part 
of  inflammable  air,  then  pure  or  dephlogisticated  air  is  composed  of 
water  deprived  of  its  phlogiston,  and  united  to  some  elementary 
heat." 

Is  not  this  passage  as  clear,  precise,  and  intelligible  as  Lavoisier's 
conclusions? — {Note  by  Mr.  Wait,jun.) 

The  obscurity  complained  of  by  Lord  Brougham  in  the  theoretical 
conceptions  of  Watt  and  of  Cavendish  appears  to  me  unfounded.  In 
1784  they  knew  how  to  prepare  two  permanent  and  very  dissimilar 
gases.  Those  two  gases  were  by  some  distinguished  as  pure  air  and 
inflammable  air;  by  others  as  dephlogisticated  air  and  phlogiston ; 
by  others,  finally,  as  oxygen  and  hydrogen.  By  the  combination  of 
dephlogisticated  air  and  phlogiston,  they  generated  water  weighing 
as  much  as  the  two  gases.  Thenceforward  water  was  no  longer  a 
simple  body;  it  was  composed  of  dephlogisticated  air  and  phlogiston. 
The  chemist  who  deduced  this  conclusion  might  have  false  ideas  on 
the  internal  nature  of  phlogiston  without  its  casting  any  uncertainty 
on  the  merit  of  his  first  discovery.  Has  it  been  even  now  mathemati- 
cally demonstrated  that  hydrogen  (or  phlogiston)  is  an  elementai-y 
body ;  that  it  is  not,  as  Watt  and  Cavendish  for  a  time  supposed,  the 
combination  of  a  radical  witii  a  little  water  V— (.Vote  by  M.  Arago.) 


478  JAMES    WATT. 

more  distinct  terms  than  Cavendish  did  in  his  Memoir  read  to 
the  Royal  Society  in  January,  1784.  By  noticing  also  the 
disengagement  of  latent  heat  in  the  operation,  Watt  added 
very  much  to  the  clearness  of  his  conception. 

3.  There  is  no  proof,  there  is  not  even  any  assertion 
■whence  it  would  result,  that  the  theory  of  Cavendish  (Blag- 
den  calls  it  conclusion)  was  communicated  to  Priestley  pre- 
viously to  Watt's  delivering  his  ideas  in  the  letter  of  the  26th 
of  April,  1783  ;  and  still  more,  nothing  leads  one  to  suppose, 
especially  after  reading  Watt's  letter,  that  he  had  ever  heard 
any  thing  relative  to  the  composition  of  water  either  from 
Priestley  or  from  any  other  person. 

4.  Watt's  theory  was  known  by  the  Fellows  of  the  Royal 
Society  several  months  before  the  conclusions  of  Cavendish 
had  been  committed  to  paper  ;  eight  months  before  the  Me- 
moir of  that  chemist  was  presented  to  that  same  Society.  We 
can  go  farther,  and  deduce  from  facts  and  dates  now  before  us, 
that  Watt  was  the  first  to  speak  of  the  composition  of  water  ; 
that  if  any  one  was  anterior  to  him,  there  is  no  proof  of  it. 

5.  Finally,  a  repugnance  to  abandon  the  doctrine  of  phlo- 
giston, a  sort  of  timidity  in  separating  from  an  opinion  so  long 
established,  so  deeply  rooted,  prevented  Watt  and  Cavendish 
from  rendering  complete  justice  to  their  own  theory  ;  whilst 
Lavoisier,  who  had  broken  through  those  trammels,  was  the 
first  to  present  the  new  doctrine  in  all  its  perfection.* 

It  might  be  very  possible  that  without  knowing  any  thing  of 
their  respective  labours,  Watt,  Cavendish,  and  Lavoisier  had 
nearly  at  the  same  time  made  the  great  step  of  concluding 
from  experiment,  that  water  is  the  product  of  a  combination 

*  No  one  ought  to  have  expected  from  Wntt,  writing  and  publish- 
ing for  the  first  time,  exposed  to  the  cares  of  an  immense  manufac- 
tory and  of  commercial  affairs  equally  extensive,  that  he  could  vie 
with  the  eloquent  and  practised  pen  of  Lavoisier;  but  the  substance 
of  his  theory  (see  p.  333  of  his  Memoir)  seems,  at  least  to  me,  who  in 
truth  may  not  perhaps  be  an  impartial  judge,  as  luminous  and  as 
remarkable  in  expression  as  the  conclusions  of  the  illustrious  Frni.ch 
chemist.— (A'b/c  Inj  Mr.  Woll^ijun.) 


LORD    brougham's    APPENDIX.  479 

of  the  two  gases  so  often  quoted.  Such  is,  in  short,  with  more 
or  less  distinctness,  the  conclusion  that  the  three  learned  men 
presented. 

It  now  remains  to  consider  Blagden's  declaration,  from 
which  Lavoisier  might  have  learned  the  theory  of  Cavendish, 
even  before  he  had  made  his  principal  experiment.  Blagden 
inserted  this  declaration  in  Cavendish's  own  Memoir  ;  *  it  was 
published  in  the  Philosophical  Transactions,  and  it  does  not 
appear  that  Lavoisier  ever  contradicted  it,  however  irrecon- 
cilable it  was  with  his  own  recital. 

Notwithstanding  all  Blagden's  susceptible  jealousy  in  favour 
of  the  priority  of  Cavendish,  there  has  not  been  on  his  part  a 
single  allusion  from  which  one  might  deduce  that,  before  pub- 
lishing his  own.  Watt  had  heard  of  his  competitor's  theory. 

We  will  not  be  so  positive  relative  to  the  question  of  Cav- 
endish having  had  some  knowledge  of  Watt's  labours,  before 
arranging  the  conclusions  in  his  own  Memoir.  To  maintain 
that  Cavendish  was  not  ignorant  of  Watt's  conclusions,  we 
might  remark  how  very  improbable  it  was  that  neither  Blag- 
den nor  any  one  else  to  whom  those  conclusions  were  known, 
had  ever  mentioned  them  to  him.  It  might  also  be  said  that 
Blagden,  even  in  those  portions  of  the  Memoir  that  were  writ- 
ten in  his  own  hand,  and  intended  to  claim  the  priority  for 
Cavendish  against  Lavoisier,  nowhere  affirms  that  the  theory 
of  Cavendish  was  conceived  before  the  month  of  April,  1783, 
although  in  another  addition  to  his  friend's  original  Memoir 
there  is  a  quotation  relative  to  Watt's  theory. 

Since  the  question  as  to  the  epoch  when  Cavendish  drew 
conclusions  from  his  experiments,  is  enveloped  in  great  ob- 
scurity, it  may  be  of  some  utility   to  inquire  what  were   this 

*  A  letter  to  Professor  Crell,  in  which  Blagden  gave  a  detailed  ac- 
count of  the  discovery,  appeared  in  the  Annalen  of  1786.  It  is 
remarkable  that  in  this  letter,  Blagden  says  that  he  communicated 
to  Lavoisier  the  opinions  of  Cavendish  anclof  Walt,  and  that  this  lat- 
ter name  figures  here  for  the  first  time  in  the  confidential  verbal 
recitals  of  the  Secretary  of  the  Royal  Society. — (Note  by  Mr.  WaLt,jun.) 


480  JAMES    WATT. 

chemist's  habits  when  he  communicated  his  discoveries  to  the  • 
Royal  Society. 

A  Committee  of  that  Society,  to  which  Gilpin  belonged, 
made  a  series  of  experiments  on  the  formation  of  nitric  acid. 
This  Committee,  placed  under  the  direction  of  Cavendish, 
sought  to  convince  those  who  doubted  of  the  composition  of 
the  acid  in  question,  incidentally  indicated  in  the  Memoir  of 
January,  1784,  and  afterwards  more  at  length  in  a  Memoir  of 
June,  1785.  The  experiments  were  made  between  the  6th 
of  December,  1787,  and  the  19th  of  March,  1788.  The  date 
of  the  reading  of  Cavendish's  Memoir  was  the  1 7th  of  April, 
1788.  The  reading  and  the  printing  then  occurred  within 
less  than  a  month  of  the  completion  of  the  experiments. 

Kirwan  presented  his  objections  to  Cavendish's  Memoir 
relative  to  the  composition  of  water,  on  the  5th  of  February, 
1784.  Cavendish's  answer  was  read  on  the  4th  of  the  follow- 
ing March. 

The  experiments  on  the  density  of  the  earth  occupied  the 
interval  between  the  5th  of  August,  1797,  and  the  27th  of 
May,  1798.  The  date  of  the  reading  of  that  Memoir  was  the 
27th  of  June,  1798. 

In  the  Memoir  on  the  eudiometer,  the  experiments  quoted 
were  made  in  the  latter  half  of  1781,  but  the  Memoir  was  not 
read  till  January,  1783.  Here  the  interval  was  greater  than 
in  the  preceding  communications.  From  the  nature  of  the 
subject,  however,  it  is  probable  that  the  author  undertook 
fresh  experiments  in  1782. 

Every  thing  renders  it  probable  that  Watt  conceived  his 
theory  in  the  course  of  a  few  months  or  even  of  a  few  weeks 
prior  to  April,  1 783.  It  is  certain  that  this  theory  was  con- 
sidered by  him  as  his  property,  for  he  did  not  allude  to  any 
anterior  or  analogous  communication ;  nor  does  he  say  that 
he  had  heard  of  Cavendish  having  come  to  similar  conclu- 
sions. 

"We  cannot  believe  that  Blagden  would  have  heard  no 
mention  of  Cavendish's  theory  prior   to  the  date  of  Watt's 


NOTK    BY    W.    FAIRBAIRN,    F.K.S.    F.G.S.  481 

letter,  if  that  theory  had  actually  preceded  the  letter,  and 
that  he  would  not  have  been  eager  to  point  out  this  circum- 
stance in  the  additions  that  he  made  to  his  friend's  Memoir. 

It  is  well  finally  to  remark,  that  Watt  depended  entirely 
on  Blagden's  taking  care  to  correct  the  proofs,  and  attending 
to  every  thing  else  that  could  relate  to  the  printing  of  his 
Memoir.  This  is  proved  by  a  letter,  still  existing,  addressed 
to  Blagden.  Watt  saw  his  Memoir  only  after  it  had  been 
printed. 


The  notes  by  Mr.  Watt,  jun.,  made  part  of  a  manuscript 
which  was  sent  me  by  Lord  Brougham  ;  and  it  is  at  the  ex- 
press request  of  my  illustrious  co-academician  that  I  have 
had  them  printed  as  a  useful  commentary  on  his  work. 


NOTE  BY  W:  FAIRBAIRN,  F.R.S.,  F.G.S. 

Ix  writing  his  historical  eulogy  of  James  Watt,  the  dis- 
tinguished French  philosopher  has  allowed  his  partiality  for 
his  countrymen  to  overstep  the  boundaries  within  which 
an  impartial  writer  should  be  resti-ained.  To  associate 
Dr.  Papin  as  a  coadjutor  of  Watt  in  the  discovery  and 
invention  of  the  steam-engine,  is  to  give  to  the  former  a  de- 
gree of  prominence  to  which  he  is  certainly  not  entitled ;  and 
it  is  much  to  be  regretted,  that  men  in  so  high  a  position 
as  Arago,  with  minds  so  imbued  with  the  love  of  truth,  and 
the  desire  to  award  to  individual  merit  the  praise  justly  due 
to  labours  in  the  field  of  discovery,  should  be  so  biassed  by 
love  of  country  as  to  endeavour  to  curtail  the  merits,  and  to 
divide  the  honour  which  exclusively  belongs  to  one  who  has 
done  more  for  practical  science,  and  for  the  great  family  of 
mankind,  than  any  other  person  since  the  days  of  Newton. 

Papin  was  contemporary  with  Newton,  and  laboured  in  the 
same  field  as  Savery,  in  experiments  on  the  effects  of  steam 

SEC.    SER.  21 


482  JAMES    WATT. 

as  a  motive  power  ;  but  we  have  yet  to  learn  that  that  power 
■was  ever  applied  by  him  to  the  organic  parts  of  an  engine, 
calculated  to  overcome  the  resistance  of  a  load,  such  as  the 
propulsion  of  machinery  or  the  raising  water  from  mines. 
The  discovery  of  an  element  of  power  is  a  totally  diflerent 
thiuT  to  its  application  through  the  organic  parts  of  a  machine. 
The  first  is  the  result  of  experimental  research  in  the  labora- 
tory ;  the  second  is  the  result  of  toilsome  labour  in  the  work- 
shop, in  the  actual  production  of  a  machine  ;  merit  for  the 
former  belongs  to  Dr.  Papin,  for  the  latter,  exclusively  to 
Newcomen  and  James  Watt. 

Savery  constructed  an  engine  for  raising  water  upon  the 
principle  of  condensation.  It  consisted  of  two  vessels, — a 
boiler  and  a  condenser,  if  we  may  so  term  them,  the  latter 
being  connected  by  pipes  with  the  water  in  the  mine  and  the 
reservoir  to  which  it  was  to  be  raised.  Under  the  boiler  a  fire 
■was  lighted,  and  the  steam  was  allowed  to  fill  the  condenser ; 
the  connection  with  the  boiler  was  then  cut  off,  and  a  jet  of 
cold  water  thrown  into  the  condenser,  which  at  once  created 
a  vacuum ;  the  pressure  of  the  atmosphere  now  forced  the 
water  from  a  depth  not  exceeding  30  feet  in  the  mine,  into 
the  condenser,  where  it  was  retained  by  a  valve.  Steam  from 
the  boiler  then  forced  the  water  from  the  condenser  upwards 
through  the  pipe  to  the  reservoir  above,  and  as  soon  as  it  was 
attain  filled  with  steam,  the  process  was  repeated.  This  slow 
and  tedious  operation  was  regulated  by  hand,  but  that  could 
only  be  done  under  the  limits  stated  above,  and  with  an  enor- 
mous consumption  of  fuel.  This  was  the  apparatus  adopted 
by  Savery,  but  we  have  no  satisfactory  information  that  Dr. 
Papin  ever  constructed  an  engine  worked  by  steam ;  his  at- 
tempts were  made  on  models  which  were  never  usefiilly 
applied;  and  Dr.  Hooke,  in  his  correspondence  with  New- 
comen and  the  Royal  Society,  pointed  out  the  absurdity  and 
fallacy  of  the  air-pipes  and  pistons,  which  he  proposed  as  a 
means  of  raising  water  from  mines.  The  only  real  inventor, 
antecedent  to  Watt,  was  Newcomen,  who  introduced  the  open 
top  cylinder,  and  the  reciprocating  motion  of  the  piston  and 


NOTE    BY    AV.    FAIRBAIKN,  F.R.S.    F.G.S.  483 

beam.  The  apparatus  antecedent  to  this  scarcely  deserved 
the  name  of  engine,  still  less  should  it  be  considered  the  parent 
of  the  modern  steam-engine.  Nevvcomen's  engine  first  ac- 
quired the  character  of  an  automaton  (however  rudely  formed) 
from  the  ingenious  application  of  the  boy  Potter,  while  its  sub- 
sequent developments,  far  surpassing  in  number  and  impor- 
tance all  that  had  preceded,  are  exclusively  due  to  James 
Watt.  Newcomen  invented  the  engine  as  it  was  when  Watt 
repaired  the  far-famed  model  belonging  to  the  Glasgow  Uni- 
versity—a mere  pumping  machine ;  Watt  made  it  a  source  of 
motive  power  capable  of  application  in  every  situation  and  for 
every  kind  of  work ;  and  it  was  in  his  hands  that  it  received 
the  name  and  properties  it  now  possesses,  as  the  most  extra- 
ordinary invention  of  all  time. 

Arago  arrogates  to  Papin  the  merit  as  if  his  discoveries  had 
led  to  the  mechanical  arrangements  of  the  steam-engine,  or 
to  the  invention  of  condensation  in  a  separate  vessel.  Now  it 
is  evident  that  Watt  was  not  in  any  way  indebted  to  hkn,  even 
for  a  hint  in  the  attainment  of  these  results.  Papin  was  not 
even  capable  of  devising  the  mechanical  arrangements  of  an 
engine,  as  it  issued  from  the  hands  of  Watt ;  and  even  New- 
comen's  was  so  rude  an  attempt,  that  the  present  steam-engine 
may  be  safely  considered  as  the  exclusive  invention  of  James 
Watt 

It  is  highly  interesting  and  exceedingly  curious  to  trace  the 
progressive  developments  of  this  machine,  as  it  acquired,  by 
slow  but  certain  stages,  its  present  proportions  and  power. 
The  constant  study,  unwearied  application,  and  experimental 
research  which  distinguished  every  step  made  in  advance, 
■will,  to  the  end  of  time,  uphold  the  name,  and  exhibit  the 
untiring  energy,  of  the  man  who  produced  so  important — so 
various  results. 

It  is  unbecoming  in  a  great  man  and  a  great  nation  to  at- 
tempt to  drag  forward  competitors  where  no  competition  exists, 
— where,  in  fact,  the  inventor  stands  alone  as  the  benefactor 
of  the  human  race.     If  Watt  had  done  no  more  than  the  in- 


484  JAMES    WATT. 

troduction  of  his  condenser,  wliereby  he  gained  one  of  the 
greatest  steps  towards  making  the  engine  what  it  is,  quad- 
rupled its  power,  and  gave  to  it  the  docility  and  powers  of 
adaptation  of  almost  animal  existence, — if  he  had  done  no 
more  than  this,  he  was  entitled  to  a  world's  gratitude,  and 
to  all  the  honours  of  an  original  inventor.  But  it  was  not 
this  that  marked  the  fertility  of  his  mind,  but  the  perfec- 
tion of  his  engine  by  an  organization  which  has  made  it 
so  powerful  and  yet  so  perfect,  which  has  given  it  a  smooth- 
ness of  action  and  almost  vital  adaptability  to  every  kind 
of  work,  and  which  will  ever  excite  the  admiration  of  every 
mind  conversant  with  the  beauty  of  mechanical  design. 

So  valuable  an  invention  did  not  escape  constant  piracj*. 
Engines  began  to  be  erected  on  the  principles  of  separate 
condensation,  which  not  only  infringed  the  patent  rights,  but 
from  their  miserable  construction  brought  discredit  on  engines 
as  a  class  ;  so  that  Boulton  and  Watt  were  compelled  at  last, 
however  reluctantly,  to  commence  a  long  series  of  legal  pro- 
ceedings, which  at  length  fully  established  the  validity  of  their 
patent. 

To  show  the  progress  that  was  made  in  the  construction  of 
engines,  and  the  immense  importance  of  their  manufacture, 
we  quote  from  a  recent  work  on  the  Mechanical  Inventions  of 
James  Watt,  by  James  Muirhead,  Esq.,  the  number  of  engines 
constructed  at  Soho. 


'■^Memorandum. 

Soho  Foundry,  16tli  March,  1854. 
"  The  number  and  power  of  the  engines  made  by  Messrs. 
Boulton,  Watt,  and  Co.,  to  the  date  January,  1824,  were  thus 
reckoned  by  the  late  Mr.  Boulton  and  Mr.  Creighton  (one  of 
his  assistants  at  Soho)  : — 


NOTE    BY    W.    FAIRBAIRN,    F.R.S.    F.G.S.  485 

Nominal  Power  of  living 

Engines.  Horse-power.  Horses  required  to  do 

the  same  work. 
283  for  pumping  and  blowing  11,247X4  44,988 

805  rotative         .         .         .12,618X3  37,854 

76  boat  engines  .         .     2,080X3  6,240 


1,164  25,945  89,082 


"And  between  January  1824  and  January  1854,  the  num- 
bers are  the  following  : — 

34  for  pumping  and  blowing    2,403X4  9,612 

164  rotative  .         .         .     7,517X3  22,551 

243  boat  engines  .         .15,358X3  46,074 


441  25,278  78,237 


"  Giving  the  following  total  numbers  : — 

1,164 25,945 

89,082 

441       .         .         •         .         .  25,278 

78,237 

1,605  51,223  167,319 


"  The  first  engine  seems  to  have  been  made  for  Bedworth, 
in  1776." 

It  will  be  noticed  that  for  pumping  engines  the  nominal 
horse-power  is  multiplied  by  four  to  give  the  real  horse-power 
required  to  do  the  same  work  in  the  same  time  ;  and  this  is 
on  the  supposition  that  a  horse  can  work  only  six  hours  a  day, 
whilst  the  engine  can  work  twenty-four.  But  in  rotative  en- 
gines an  allowance  has  been  made  in  the  above  table  for  loss 
of  power  in  the  action  of  the  crank,  &c.  as  compared  with  the 
direct  action  in  the  other  case,  and  the  nominal  horse-power 
is  multiplied  by  three  only. 

Perhaps  it  would  be  more  accurate  to  suppose  that  a  horse 
can  work  for  eight  hours  out  of  the  twenty-four ;  but  at  the  same 
time  to  multiply  the  nominal  horse-power  by  two,  because 


486  JAMES    WATT. 

each  indicated  horse-power  of  the  engine  =  33,000  lbs.  raised 
one  foot  high  per  minute,  is  at  least  twice  as  much  as  its 
nominal  power,  or  twice  as  much  as  an  ordinary  horse  could 
work  up  to.  We  shall  then  find  that  it  would  require  no  less 
than  250,974  living  horses  to  perform  the  work  of  the  engines 
constructed  by  Messrs.  Boulton  and  Watt  up  to  January 
1854. 

One  of  Watt's  fellow  labourers  should  hardly  be  passed  over 
in  any  statement  connected  with  the  steam-engine ;  we  allude 
to  the  late  Mr.  William  Murdock,  whose  vast  practical  knowl- 
edge was  employed  in  carrying  out  the  designs  of  Watt  for 
upwards  of  half  a  century.  Mr,  Murdock  directed  the  appli- 
cation of  the  new  steam-engines  to  drain  the  water  of  the 
Cornish  mines.  In  order  to  adapt  that  moving  power  to  ex- 
hausting pumps,  and  to  establish  the  system  in  mines  of 
extreme  depth  inundated  by  appalling  quantities  of  water, 
great  skill  in  practical  mechanics  was  requisite.  Mr.  Murdock 
showed  that  he  had  sufficient  resources  of  genius  and  wisdom 
of  experience  to  triumph  over  every  difficulty.  He  was  the 
introducer  of  the  system  of  lighting  by  coal  gas,  and  for  his 
paper  on  that  subject  sent  to  the  Royal  Society  he  received 
the  Rumford  gold  medal.  He  was  also  the  patentee  of  some 
new  methods  of  constructing  steam-engines,  &c.,  and  his  sug- 
gestions often  enriched  the  Soho  machinery.  We  have  there- 
fore great  pleasure  in  bearing  testimony  to  the  merits  of  one 
of  our  first  practical  mechanics,  the  able  assistant  and  coadju- 
tor of  James  Watt. 

W.  F. 


THE    END. 


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